The Handbook on Plumeria

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Plumeria Culture

 

Plumerias are among the world's easiest plants to propagate, grow and flower. They are so easy, in fact, that we know of no other plant that will give so many months of fragrant and colorful rewards for so little effort. This section is devoted to sharing our knowledge and that of many of our friends to assure you of success in all areas of plumeria culture. We have files full of letters telling us how easy they are to grow. One of the most illuminating is from Marcia Todd Romberg of Austin, Texas. We quote excerpts from her letter of July 1986 to open this section:

I have grown plumerias in Austin and Dallas for more than twenty years and have never had one fail to bloom prodigiously all summer, have any insect or other problems, or any cutting fail to grow and bloom. ... I have real difficulty in convincing the people I give these to that they are the easiest plant in the world to grow. Whenever they have failed it was because people won't believe me and give too much loving care.

Mine are set out (either in the ground or in pots) after the last possible frost date (usually about April 1 here). They are put into ordinary garden soil (Austin's is highly alkaline) with lots of compost. During the summer they get only the routine lawn watering and since we are almost always on water rationing here that can be only every five days. They bloom heavily all summer and frequently set seed although I have never grown any from seed.

When a few of the leaves begin to turn yellow in the fall (and always before November 15) the plants (which have incredibly small root systems for their total size) are lifted with whatever soil clings and set into plastic garbage bags and set into a garage heated only by the presence of the hot water heater. No watering all winter.

You said you wanted to hear of other grower's delight—of frustrations I have none.

 

PROPAGATION

 

Plumerias may be propagated from seeds, cuttings, air-layering or grafting. All "methods assure you of success, but the first two are the easiest.

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Seeds

 

The seed pods of plumerias are correctly known as follicles and somewhat resemble two downward curving horns. In tropical areas follicles ripen throughout the year but are most abundant in spring. They should be allowed to ripen as fully as possible or the tree which takes up to eight or nine months. In temperate climates, follicles (here after called pods for simplicity), often break off before maturity since their stems otter do not have enough strength to hold them. This is especially true of plants grown in containers. If you would like to propagate seeds from one of your plants be sure to support the weight of the ripening pods with a plastic tie.

It is interesting to note that we have never seen a pod break off in the tropics. No doubt the longer growing season and the fact that plants are in the ground are contributing factors toward stronger plants. If you do have one break off before it has fully matured, allow it to ripen in a warm, dry place. If it splits open or dries enough for you to split it open, feel the seeds inside. If the seeds are plump and there is no evidence of fungus attack, there is a good chance they will be viable. One can often save pods in this way, especially if they are within a month or so of ripening.

When a pod splits open it will reveal perfectly aligned rows of seeds. Remove the soft, cork-like endosperm tissue and lift out the seeds. Each seed is covered with ; tough, membranous brown sheath with a papery wing of the same size or larger. The seeds will lay in overlapping rows beginning from the tip of the pod. Half a pod ma' contain more than 50 seeds!

Some plumerias rarely develop pods, others produce numerous pods with sterile or mostly sterile seeds (this was true of Plumeria alba in India), and some produce a very high percentage of viable seeds. Plumeria seeds can remain viable for more than a yea1 under good storage conditions and sometimes for 2 to 3 years.

An interesting discovery was made by Elizabeth Thornton who sprayed gibberelic acid on newly emerging flower buds {Vs to V4 inch high) and found that seed se increased.

 

Testing for Viability

 

Take a seed between thumb and forefinger and squeeze it lightly. It should fee, plump and solid to the touch. After discarding flat and dessicated seeds, select at ran dom from among the remainder and cut one or two open. If the embryo is cream white and fleshy the seeds are viable, if dry and hard, or brown, they have lost their viability.

 

Planting Media for Seeds

 

In the tropics we planted seeds in a light, porous, fully sterilized medium. We sifted compost, added sand and topsoil, mixed all the ingredients in proportion and then sterilized. Here in the U.S. things are so much easier. One can purchase any number  of quality potting soils already sterilized and pre-mixed. These are generally light • weight "soilless" formulations containing sphagnum peat moss and perlite, (occasionally some vermiculite), to provide good aeration and drainage with just the right amount of moisture retention,

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There are a few important keys to success. Seed trays need only be 3 to 4 inches deep but must have plenty of holes for drainage. One of the most important things to remember is to moisten the planting medium thoroughly prior to planting the seeds. This is necessary because mixes high in peat generally do not accept water readily or evenly unless a wetting agent has been previously added to the mix. Place seed trays in morning sun or filtered light for best germination.

 

Successful Germination

 

One of the real secrets of success, both for germinating seeds and for rooting cuttings, is soil temperature. A cold, damp soil does nothing to encourage germination of seeds or root formation in cuttings and often has the effect of rotting both. Be sure the soil is warm before attempting to germinate plumeria seeds. An ideal temperature is around 80 degrees. During the past three years we have made a number of experiments with bottom heat (see paragraph on Planting the Cutting), and can report an unqualified success with both seeds and cuttings. We have also used grow-bulbs approximately 6 inches above the soil with excellent results.

 

Planting the Seeds

 

Following are three methods for planting plumeria seeds:

Method 1:

This method has proven successful for many growers in temperate and sub- tropical climates. Plant seeds with the wing upright and completely out of the soil, as if the seed had dropped down to earth and embedded itself only to the depth at which the wing begins.

 

Method 2:

This is a simple method that has also proven quite successful. Lay the seeds between two thicknesses of moistened paper towels. As soon as the seeds germinate they may be transplanted into small individual containers.

 

Method 3:

This is the best method we have found for successfully germinating plumeria seeds. Plant them horizontally about '/s inch deep, or about twice the thickness of the seed. Planting too deep inhibits germination and planting too shallow causes the seeds to rise to the surface. Perhaps the best rule-of-thumb is the salt and pepper analogy—even if you pour on the salt and pepper, it will never be more than a light coating! After covering the seeds, firmly tamp the medium. The importance of good soil contact cannot be overemphasized. Give seedlings plenty of room; preferably 2 to 3 inches apart.

 

Watering Seeds and Seedlings

 

Damp-off, a fungus that attacks and destroys young seedlings with extreme rapidity, is caused by overwatering and crowding of seedlings by planting seeds too close

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together. Plumeria seeds are not especially prone to damp-off, but as a general rule one should be careful about watering too much and planting too close. In fact, more plants are killed by TLC (over-watering is first in this category), than any other cause!

Since the medium has been thoroughly moistened before planting, a light sprinkling should be sufficient to keep the soil damp until germination. The finer the sp ay the better so as to disturb the soil as little as possible. Once the seeds have geminated, water moderately. As plants begin to exhibit rapid growth, water thoroughly then allow the mix to dry until it is just slightly damp before watering again. You will get excellent results with a weekly application of a water soluble fertilizer at half strength.

 

Germination

 

Plumeria seeds germinate quite rapidly, pushing vigorously through the soil, of en within three days and usually not more than a week or ten days. We always allow at least two weeks to be sure that all the slow starters have had a chance to emerge, "he percentage of germination should be very high, usually not less than 70% and up to 100% for select seeds.

As the seedling emerges from the soil the sheath will be attached. As growth progresses, the developing plant will vigorously throw off this tough, fibrous membrane to reveal the cotyledons or "seed leaves". If the seedling should not be strong enough to push off the sheath you can help by moistening it and gently peeling it off. If not removed the seedling will turn brown and die. Although we never had to remove a sheath in the tropics where seedlings easily thrust off their encasement, we have encountered the problem here in Houston.

Pros and Cons of Propagating from Seed

In summary, there are several advantages and disadvantages in propagating plumerias from seed. First, the plus side! Seeds are easily handled and a large number of plants can be started in a small space with relatively little expense. Most important : is the fact that all new cultivars must be produced from seed. Plumeria seedlings have more variability that any plant we know. Plant twenty seeds from the same pod  and you are likely to get twenty different combinations of color, size and form, some resembling the female parent, others exhibiting totally different characteristics. If' you have collected seeds from a superior parent with a number of desirable qualities such as size, color, shape, fragrance, and substance, you have an excellent chance of producing a hybrid of merit.

Dr. James L. Brewbaker, Professor of Horticulture and Genetics at the University of Hawaii at Manoa, was very helpful in building the plumeria collection at the Matrimandir Gardens by sending seeds from outstanding cultivars in Dr. Criley's plumeria collection. Dr. Criley later wrote: "The seeds I provided you were labelled with he name of the seed parent. That is all I can tell you about their origin, except that most of the parents are P. acuminata. From observations of the breeders lines, I would  say you could expect quite a bit of variation, but most progeny will reflect the prim n colors of the parents—the pinks and whites tend to predominate."

A note on seedlings from the 1980 issue of The Planter, in an article by M. Ratnas

 

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¦abapathy of the University of Malaya and J. Mossel of the Netherlands, is worth 1 mentioning: "But, as pointed out by Stone (1970), the tap-root system of plants raised from seeds would confer an important advantage over propagation by cuttings."

What then are the negatives to growing plants from seed? From thousands of seeds of unknown origin one would be very fortunate to get more than a few cultivars superior to any of the named varieties available today. Almost all seeds available today are from unknown parentage. Many will be from inferior stock and the results may be disappointing. Also, for those interested in immediate gratification, the 3 to 4 year wait for flowers may be discouraging. Yet, the field is still wide open, the possibilities are unlimited and new cultivars are sure to emerge surpassing all we have seen to date.

 

From Seed to Flower

 

The timetable given by most of the expert plumeria growers we have met is usually 3 to 4 years. Given the long growing season we were fortunate to have in India (365 days to be exact!), we had phenomenal results with our seedlings. Most flowered in less than 2 years and we had one seedling from Hawaii flower in just over 10 months!

The conclusion: Give seedlings plenty of light and heat throughout the year; grow them under lights in winter, if possible; plant in organically rich, well-drained soil; feed and water generously during the growing season. Providing these conditions could reduce the waiting time as much as 40%.

 

An Additional Note on Seedlings

 

When a seed germinates, the first leaf-like appendages it produces are the cotyledons or "seed leaves". These are not true leaves, and in most cases do not resemble them, but are food storage organs that nourish the plant in its initial stage of growth. The best time to transplant is when the seedling has 2 or 3 sets of true leaves. Since plumeria seedlings grow at a fast pace it is best to transplant immediately into a 6 or 7 inch pot.

 

cuttings

 

This is the easiest way to propagate plumerias and the fastest way to have plants in bloom. Even though propagation by cuttings is relatively foolproof, there are important considerations both in taking cuttings and in rooting them. Cuttings should only be taken from mature wood that is firm and grey in color. Immature cuttings of green wood are extremely difficult to root and are not recommended for the beginner. The ideal time to root cuttings is in late spring when soil temperature as well as air ternperature has warmed sufficiently. With the techniques listed below, we have been able to successfully extend the rooting period from early spring through late summer with the same degree of success.

 

Type and Size of Cuttings

 

Tip cuttings 12 to 15 inches long with a diameter of ¥4 to 1 inch are ideal. Stem cuttings (see Appendix A) have an open cut on the top and are susceptible to rot from

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rain or watering. Tip cuttings (literally, the tips of the branches), can be taken at any length desired as long as they include 3 to 4 inches of grey wood. Well-branched rut tings as large as 6 feet in length are easily rooted following the basic principles listed in this chapter.

 

Preparing the Cutting

 

After making a cutting, take the following steps:

Remove all large leaves in order to reduce transpiration and allow the energy to go into root formation. After the leaves are removed the latex will dry quickly and seal the tip. We have seen several cultivars that have such strength that their leaves and inflorescences may be left on while the cutting is rooting but this is recommended only for the experienced grower. In general it is best to remove all or most of the leaves and not allow the cutting to flower. (Many cuttings have a latent inflorescence that will emerge after the cutting is taken from the parent plant.)

If the base of a cutting has any jagged edges it is best to cut it cleanly. Cutting the base at a 45 degree angle will provide somewhat more surface area for callus forma- tion, but the most critical point to remember is to allow the base of the cutting to dry thoroughly, at least 3 to 5 days (some growers recommend 2 to 3 weeks!). Drying should take place in a warm, shaded area protected from rain and moisture.

 

Types of Rooting Media

 

In more than twenty years of propagating plumerias from cuttings, we have experimented with a multitude of media and have had varying degrees of success. Our only failure (almost total) was with a predominantly vermiculite-based planting mix that held too much water. We would also caution against using soil since water retention is too great and the medium is not sterile or sufficiently porous to allow easy penetration of roots. Early experiments were with coarse sand gathered from the upper areas of beaches where the rain had leached away the salt over a period of years. Sand worked very well since there was no resistance to root formation but there were two draw- backs due to its weight. Not only were the pots very heavy to lift, but in trying to remove the cuttings when rooted, the tender, young roots would break off. Newly formed plumeria roots are extremely brittle and will snap off at the slightest disturbance. It is interesting to note that a friend in Hawaii, Jim Little, finds that beach sand, even with salt in it, is still one of the best mediums for rooting plumerias. As to the question of roots breaking due to the heaviness of sand, we were helped by another friend, James D. Jones, Jr., of Dallas, Texas. (This would apply only to a few cuttings planted in a container where the overall weight was not too much to lift.) James writes "... a very simple solution . . . which works very effectively for anything rooted in sand. Take a container of warm water, submerge the rooted cutting in its pot, gently lift cutting out. The water allows the roots to be released without damage."

Experiments in India were with coir dust, the peat-like residue from the coconut husk. We found it to be an ideal replacement for peat with almost identical moistureholding characteristics as well as the soft fibrous quality so unique to peat moss. Coir dust, or "coconut peat" as I termed it, is a lightweight medium, easily handled, ' na loose enough for roots to form rapidly without resistance. We could dig down into the

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medium with our fingers and come up with a ball of roots every time.

Our success with coir dust in India led us to try peat moss here in Houston. Although this may seem hard to believe, Houston has a much cooler climate than South India, even in the summer! Since peat moss holds nearly 600 times its weight in water, we found the moisture retention was too great for plumerias. We then began blending coarse perlite with the peat and this worked very well. Still, it is easy to overwater so we cut back the peat even more. Our recommendation is % coarse perlite and Vi peat. The moisture-holding capacity is excellent, drainage is rapid, and cuttings don't rot even if one should be too generous occasionally with water. Although perlite is toxic to some plants, it has no adverse effects on plumerias. In fact, cuttings rooted in 100% perlite will develop a mass of roots. The bottom line is to achieve a lightweight medium that combines excellent air porosity and optimum drainage while holding just the right amount of moisture, is sterile, and has a texture that allows plumeria roots to penetrate with little resistance and form a mass adhering to the medium.

 

Rooting Cuttings in Water?

 

Yes, after all you have just read, the uniqueness of plumerias is such that many people have written that they have successfully rooted cuttings in water! Since we have not personally tried this we will quote directly from friends who have. Phil Brodhag writes: "Our son had a cutting in a glass of water that has been there for about two years. It has rooted well and is now planted." Barbara Anderson of Houston has also written: "You may include my experience with rooting plumerias in water in your handbook. Just stress the importance of letting the cutting dry 24 hours or the cutting will rot. I have put cuttings in water in November and December after the leaves have fallen off and the cutting will put leaves on without roots. Then in the springtime I pot them or put them in flower beds." Finally, a very interesting note from George Slusser, a dedicated grower in Washington: "The water-rooted cutting of Plumeria came from a packaged item, purchased either at a commercial greenhouse or from a novelty store in Honolulu, Hawaii. I placed it in a clear glass jar and put it in a west window, over the kitchen sink. There was about an inch to P/2 inches of water. I used a rooting powder. ... I had no idea that water-rooting was novel for Plumeria. . . ." (Note: George has since conducted many successful experiments rooting plumerias in' water. We have included some of his excellent photographs demonstrating the results.)

With plumerias we have found that exceptions are sometimes as valid as rules!

 

Planting the Cutting

 

When planting a cutting remember, as with seeds, to pre-moisten the medium. We have found that pressing down on the medium and packing it tightly both before and after inserting the cutting leads to faster root development. It is best not to plant cuttings  too deep in order to reduce the possibility of rot. Plumerias will not produce roots from the sides of a cutting no matter how deep it is planted since all rooting takes place around the base. We prefer the simple method of filling a container with 4

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to 5 inches of mix and inserting the cutting at an angle. Some growers allow the con. tainer to support the cuttings but we find with good compaction of the medium they will hold on their own. Many cuttings may be started in the same container but do not place them too close together as this will cut down on air circulation and leap to potential problems such as fungus.

This year we found the best container yet; molded plastic baskets (available every- where) that are similar to laundry baskets but slightly smaller. We used a 16 x 21 >; 10 inch basket, but there are many sizes available. The baskets are solid on the bottom and have open slits in the sides. We drilled several V4 to 1 inch holes in the bottom in the center and at the four corners to guarantee excellent drainage. We also placed a 5 or 6 inch strip of inexpensive ground cover cloth around the inside to prevent :he medium from spilling out through the slits in the sides. We packed in about 5 inches of mix, pressing it firmly against the sides to hold the cloth in place. The two things we like most about the baskets are that they are lightweight and easily handled, and they allow plenty of air to circulate around the cuttings.

Before planting a cutting, first make a hole in the medium with a round dowel  or stick approximately the same size as the cutting. Moisten the base of the cutting, shake off the excess moisture, then dip the cutting in a rooting hormone and shake off the excess powder. After many years of trials we are convinced of the effectiveness of rooting hormones, especially on the more difficult-to-root varieties. There are many types of rooting hormones available depending on the nature of the plant material one wishes to propagate. Our recommendation is to use a rooting hormone containing fungicide. For the most challenging varieties one may use a higher strength formulation available from growers supply houses.

In 1984 I made an initial experiment in the use of bottom heat by placing cuttings in one gallon plastic pots set in saucers on top of our gas water heater. It was not really a controlled experiment since most of the time I forgot to water! Yet, all c the cuttings came through in good health and were the first to root when I put their, outside in the spring. This past year I repeated the experiment with some cuttings o' rare species. I remembered to water and to my delight the cuttings were well-rooted b fore spring. In addition to being rare, these were also difficult species to root. This s ring we had great success rooting some especially challenging varieties by using a propagation mat with a thermostat that kept the soil temperature at a constant 80 degree .

 

The Rooting Process

 

The first stage of the rooting process is the formation of callus tissue at the base of the cutting. Because of the strong life-force in a plumeria cutting, callus tissue  can often be seen forming at the base of cuttings that have been left out to dry for a long as 2 to 3 weeks after being removed from the parent plant. Callus tissue is white creamy-white, almost translucent, and builds up around the base of a cutting. The tissue will often emerge only at one part of the base, at other times it will encircle Brittle white roots will emerge soon after the development of this tissue. Cutting should not be disturbed during the rooting period in order to prevent shock  and

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damage to new roots. Once started, roots develop quickly and densely and will become less brittle as they mature.

 

catering Cuttings

 

With the new rooting mix formula we have developed there is much less chance of cuttings rotting due to overwatering. Watering once a week throughout most of the rooting Period should be sufficient unless you are certain the medium has become dry throughout. Since the water retention of different mixes will vary considerably, it is best to develop a "feel" for the amount of water required. You can begin by testing with your finger, digging as deeply into the container as possible to feel whether the medium is wet, damp or dry. This takes some experience but stay with it and you'll develop the touch! If you feel insecure, a water meter with at least a 6 to 8 inch probe will be the best way to ascertain the proper moisture content. Ideally, the rooting medium should be damp but not wet, except when you water, and then you should soak the medium thoroughly. An exception would be the difficult-to-root cultivars, especially some of the red shades, which should be kept a bit on the dry side. On a scale of 1 to 10, with 1 being completely dry and 10 saturated, we would recommend keeping the moisture content between 5 and 6 for most cuttings and between 4 and 5 for the more challenging varieties. Moisture meters are calibrated in the same way.

 

Sun/Shade Requirements for Rooting Cuttings

 

Since we first published our handbook in 1985, we have conducted numerous experiments in light requirements for rooting cuttings. This spring we started cuttings in full sun, filtered light and under clear fiberglass. We found no appreciable difference in any of the exposures. We recently started cuttings in August under the same conditions (plus 95 degree heat and high humidity) with equal success. The only thing we would caution against is starting cuttings in dense shade where they would be more susceptible to rot through overwatering. Some growers start cuttings in the shade for a week or two and then move them into full sun.

 

Testing for Roots and Removing Rooted Cuttings

 

The next obvious question is how to know when the roots have formed sufficiently for transplanting. This can be a frustrating experience. Such is the energy in the stem of a plumeria that cuttings will often produce leaves and infloresences, exhibiting signs of vigorous growth, without even beginning to root. There is no harm in giving He cutting a very gentle tug to detect if there is resistance. Be careful, however, because a strong tug will rip off the brittle new roots. If you have any qualms about this it is best to insert your fingers down as far as possible into the medium, an inch or two from the stem of the cutting, and then pry upwards. If a root system has develoPed you can easily feel it and remove a "ball" with a minimum loss of roots. (Altough it is admittedly hard on the fingernails, no trowel has the sensitivity of your hands!) On occasion some cuttings will show no signs of rooting or leaf growth. It is best to remove- these and examine for rot at the base. If the cutting has begun to rot u can cut it back completely to green wood where no sign of brown remains, then allow it to dry thoroughly and start the rooting process over again.

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Air-layering

 

Air-layering involves more work than propagation by cuttings or seeds, but it is the surest method since the part to be rooted is not separated from the parent plant until roots have formed. One may wish to try this on rare varieties.

As with cuttings, it is preferable to make air-layerings when the plant is in an active stage of growth. It does not matter whether the branch you have chosen is flowering or not. The best time for air-layering would be from a week or two after the plant has resumed normal growth in the spring until a month before the end of sum- mer.

Be sure the branch is mature and at least 1 inch in diameter. It is best to have 12 to 18 inches of growth beyond the point where you want the roots to form. At that point, make two separate cuts encircling the branch, about I^1/2 inches apart (see Appendix A). Scrape away all of the cambium layer down to hard wood so the cut cannot heal over. Then pack a ball of moist sphagnum moss or peat moss around the cut and cover with plastic wrap or a piece of plastic bag, tying both the top and bottom securely with string or twist-ties. It will take from I^1/2 to 3 months for roots to fully develop but you will be able to see them growing through the moss. If you have wrapped the plastic tightly, you will probably not have to water the moss again.

When the roots are well-formed, cut the branch off just below the root formation, remove the plastic carefully and plant the rooted layering with the moss in a 10 or 12 inch container.

 

Grafting

 

Our first experiments with grafting were both memorable and surprisingly successful. Once again, our class of school children in Auroville participated in the experiment. (If we succeeded with six year olds holding and wrapping electrical tape and nine and ten year olds making the incisions to join stock and scion, I think everyone who is interested should give it a try!) One week our goal was to create a "Rainbow Tree" by grafting scions of different plumeria cultivars onto a semi-dwarf variety of Plumeria obtusa. We used standard grafting techniques, mainly the "whip and tongue" method, and the wedge or V-shaped graft, making certain that stock and scion were about the same diameter, then wrapped the entire area with electrical tape. To further protect the grafts from breaking we splinted the grafted area with bamboo sticks. .

For the grafting experiment we used mature wood about 12 inches in length an about 1 inch thick, taking care to be sure that the cambium layers on stock and scion were in good contact. Four to six weeks later we removed the tape to find the grafts perfectly joined. Since we did the grafting in early spring we were able to enjoy a pro fusion of color on our "Rainbow Tree" the same year!

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  FAMILY MEMBERS 

 

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petite Pink, also known in Hawaii as Dwarf  Pink Singapore.

 

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SOILS AND SOIL MIXES

 

Soil Mixes for Containers

 

Plumerias are very heavy feeders and respond best to rich, well-drained, organic soil mixes and frequent supplemental fertilizing. Whether potting or repotting, the following is an excellent formula from an expert Indian gardener, Sri Parichand, with whom we had the honor to work for many years. His 'Singapore' plumerias were the most beautifully grown pot plants we have ever seen; they were compact, usually 2 to 3 feet in height and about the same spread; the foliage a glossy, dark green, covered with intensely fragrant, pure white flowers month after month from April through October. Here is his formula:

50% well-rotted cow manure

25% leaf mold

25% good garden soil

1 handful bone meal per 12 inch pot

There are many good packaged soils and soilless products available in the U.S. We prefer an organic-based planting mix that has a high percentage of compost. In addition to bone meal, there are numerous organic ingredients that may be added to a basic soil mix such as composted manures, blood meal, rock phosphate, perlite, vermiculite, peat moss and charcoal. All have their value for certain plants but we do not recommend the addition of peat moss or vermiculite for plumerias as these tend to hold too much moisture. The planting medium must be well-drained and well-aerated.

Ingredients that are too fine will settle in time and create an oxygen depleted zone toward the bottom half of the pot and roots will not be able to grow past that point. Water stagnation and ultimately root-rot may follow. Plants have many ways of telling us they are in soil that is too heavy or poorly drained. Usually one will first see drooping leaves (not due to dryness but rather to oversaturation), or soft stems, and if one pulls the plant out of the container there will be root-rot or no root development at all.

To sum up the ideal soil mix: first, it must be rich in organic nutrients and exceptionally well-drained, yet have excellent moisture-holding capacity, with well distributed particle size throughout to avoid fines settling towards the bottom and inhibiting further root growth; finally, a good container mix will be easy to wet and have a wealth of beneficial microorganisms present to assure a slow and balanced release of nutrients.

 

Soil Preparation for Planting in the Ground

 

Planting directly in the ground is a bit less challenging than container culture but there are still a number of specifics that need to be addressed. Although plumerias will tolerate many apparently adverse conditions, they will not survive in heavy soils that tend to become waterlogged. Few soils are naturally ideal with a basic composition of well-drained, friable sandy loam possessing the following characteristics: excellent

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drainage combined with optimum moisture-holding capacity, substantial organic content, high microorganism activity, adequate NPK and trace elements in the right balance to assure sustained, vigorous and healthy plant performance. Soil pH, unless extremely unbalanced, is not very critical to plumerias since they will do well in pH ranges from neutral to slightly acid to slightly alkaline. In fact, they are very tolerant of rnany conditions in nature. In Botany of the Maya Area, Miscellaneous Papers XIV- XXI, published in 1940, there is an account of an expedition that collected specimens of Plumeria rubra from limestone hills bordering the Mountain Pine Ridge in the Yucatan Peninsula. For container planting we prefer to begin with a soil mix that is slightly acid since watering, especially with treated water, tends to raise the pH.

 

PLANTING AND TRANSPLANTING

 

Transplanting Seedlings and Rooted Cuttings

 

General rules of horticulture apply to plumerias as to any other plant. In transplanting, the main objectives are to disturb the root system as little as possible and not let the roots dry out from exposure to wind or sun. Even though plumerias are tougher than many plants, you should still follow these basic steps:

1. Have everything in readiness before removing a cutting or seedling from its container. This includes wetting the soil in the seedling or cutting pot as well as the soil in the new container. Have additional soil ready for topping up as well as plant stakes and ties.

2. It is best to transplant towards the end of the afternoon, after the heat of the day has passed. The plant will then have the cooler hours of the evening and early morning to recover from the shock of transplanting. Work rapidly, in the shade and out of the wind, allowing the least amount of time to elapse between removing the plant from the rooting medium and placing it in the new soil mix. This will insure that the roots have minimum exposure to the air.

3. Always try to remove the new plant with a good "ball" of soil around the roots, taking special care to break as few roots as possible.

4. Center the plant in the container about 1^1/2 inches below the rim and gently firm the soil on all sides. Remember to cover plumeria cuttings only just above the depth at which the roots begin. You can get away with planting slightly deeper but we have had problems on occasion with stem rot during winter storage. Since plumerias will root quickly in their new container, staking is only temporary.

5. Lastly, water thoroughly using a transplant vitamin containing Vit. Bl (Superthrive, root stimulator, etc.) to reduce shock and stimulate new growth.

 

Repotting Container Grown Plumerias

 

It is easy to repot well-established plumerias in containers, especially if one has a strong back! Actually, it is much easier to repot mature plants than rooted cuttings or seedlings. As your plumerias grow, their root systems become stronger and can form a dense mass in just one season. The brittleness disappears and individual roots become

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tough and stringy. Often they will protrude through the drainage holes in the container. This is a sure sign that you should repot. Aesthetic proportions are a second consideration. One should achieve a harmonious ratio of plant to container size. A top heavy plant in a small container has no balance (aesthetic or physical), and a small plant in a large container looks just as awkward.

The same transplanting rules given above apply to repotting, though the actual process differs somewhat. First, remove the plant from the original container. This may involve cutting some of the roots that have pushed through the drainage holes. When the roots have grown too large to get them back through the holes without tearing and scraping, cut them cleanly off at the edge of the pot. It is better to have the root ball slightly on the dry side rather than moist, the object being to remove the plant without breaking up the root ball. Lift the plant by the trunk, hold the container a few inches above the ground and tap the container with the hand (or trowel or piece of wood). The container should fall to the ground, the plant safely removed. A second method, for plants that are not too tall, is to lift the plant, turn it upside down and tap the edge of the container on any solid edge such as a wheelbarrow, workbench, etc. This should loosen the ball and the container can then be lifted off. This is a good method for transplanting from container to ground or for gently hand- ling plants with weak root balls, for after removing the container one can place both hands under the ball and lower it to an upright position. The plant can then be placed in the ground or a larger container.

On removing your plumeria from its pot, check to see if the roots are encircling each other. This is a common occurance in plants grown in containers. Once this begins it is rather like a bad habit—very difficult to break! In fact, all pot bound plants will behave in the same way and their roots will not change this circular pattern even if planted in a large hole with an ideal medium. Do not hesitate to "comb" the roots downward so they are once again in a vertical position where they can spread out into the earth. It is best to cut off the encircling roots from the bottom of the root ball with a sharp knife, or pruners. Established plumerias regenerate roots rapidly and, instead of suffering a set-back, they will be invigorated by the treatment.

 

Top-dressing and Root Pruning

 

Rather than repotting plants the second year it is easier to top-dress. This technique produces amazing results in growth and flowering with a minimum of labor. The method has been utilized in the tropics for hundreds of years, where sun and heat rapidly deplete nutrients in containers.

Remove as much soil as possible from the top of the container without damaging the roots. You will find that you can remove a fair amount of soil from a two year old plant. After removing the soil sprinkle 1 handful of bone meal around the exposed roots and cover to the original level with a mixture of 3 parts well-rotted cow manure and 1 part sandy loam. Top dressing is most effective when done during the first warm days of spring.

Another method is to root prune your plants and replace them in the same size container. With the ball on the dry side for easier removal, follow the methods listed above for repotting, then cut away about 1 inch on each side of the root ball and from

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1 to 2 inches from the bottom. Have your container mix ready and, following all the above directions for preparing containers, fill with the new medium plus a handful of bone meal, pack the soil tightly against the roots for good contact and water thoroughly,.

Root pruning is best done during the spring when new roots will regenerate rapidly but it may also be done in the fall when removing plants from containers for winter storage. Plumerias respond very well to root pruning as it is a stimulus to new growth and flowering. The technique may also help recalcitrant plants to bloom, especially if transplanted into a larger container with organically rich soil.

After transplanting, always water with a transplant vitamin and place the plant in filtered light or light shade.

 

SUN/SHADE REQUIREMENTS

 

Although there are a number of factors that will influence the amount of sun we give our plumerias, the most important thing to remember is that in nature, plumerias' grow in full sun exposures and are not found anywhere in heavy shade. We have observed plumerias under all types of sun/shade conditions and have found that unless they have an absolute minimum of one half day exposure to full sun, they will not bloom. We once planted some varieties of Plumeria obtusa along a fence line where faster growing trees eventually shaded them too heavily and the results were remarkable. Flowering diminished rapidly, limbs became weak and leggy stretching for sunlight, and finally the plants stopped flowering altogether. As a general rule the more sun one gives, the better the flowering one can expect. There are, however, exceptions; some cultivars will not tolerate the most intense afternoon sun and should be allowed to have partial afternoon shade or filtered light. Also, in areas of high air pollution, leaf burn often occurs with plumerias in full sun and plants grown in containers seem to be more sensitive than those in the ground. It may be necessary to give your plants full morning sun exposure and filtered light from about 2:00 pm. Plumerias planted in containers, especially in the southern states where the problem is more likely to occur, can be moved about until the best location is found for a particular variety.

 

WATERING

Watering Plumerias in Containers

 

Watering is a skill—or perhaps an intuition—developed over the years through an intimate contact with plants that enables one to understand their widely divergent needs. Weather conditions (sun, overcast skies, wind), time of the year, size of plants size of root mass, size and type of container, and type of growing medium are all factors that will determine the amount and frequency of water necessary. Fortunately,

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plumerias are very resilient and a missed watering will not send them into shock. A general rule for most plants is to water thoroughly and infrequently rather than shallowly at brief intervals.

Water plumerias thoroughly when the soil is dry and then allow the medium to dry out before watering again. Normally containers larger than 2 gal. need water only once a week unless temperatures are in the 90's or humidity is unusually low when they may need to be watered as often as twice a week. During periods of intense heat and drought one may have to water every other day but more than this is not necessary. Smaller containers and recently transplanted rooted cuttings or seedlings will need more frequent watering and should be monitored on a day to day basis. All plants tell us rather quickly when they are in need of water, first with flaccid leaves, then overall wilting. You will be amazed at how tolerant plumerias are, however, for they can survive neglect and absolute minimum care better than most plants.

 

Watering Plumerias in the Ground

 

Our experiences in India taught us that plumerias planted in the ground require very little water. During the long hot summers we watered mature trees only once a month, filling the 3 to 4 foot berm around the plant. Newly established trees and younger plants were watered weekly. Experiments conducted in Green Belt areas surrounding the township of Auroville determined that newly established plantings of plumerias would not survive months of drought without supplemental water. It was also found that overly generous waterings in our nursery plantings caused excessively rapid growth that developed weak and spindly limbs, easily susceptible to breaking. Overwatering promotes heavy vegetative growth and most plumeria growers would prefer flowers. If you plant plumerias in the ground, water sparingly.

 

FERTILIZING

 

Plumeria growers have discovered many different techniques that work for them. We have utilized a number of these along with some of our own tried and true methods and have come to the age-old conclusion that you should continue with whatever has been successful for you, even if the "experts" are not inclined to agree. "If it ain't broke, don't fix it", applies as much to plants as anything else!

There are, however, certain nutrient combinations and fertilizing principles that almost always produce the desired results. Plumerias thrive best with a fertilizer low in nitrogen and high in phosphorous, with ample potash and balanced trace elements, especially iron and magnesium, which help prevent chlorosis and leaf burn, respectively. Nitrogen is necessary to promote overall plant development including healthy stems and foliage, but too much nitrogen will promote vegetative growth at the expense of flowering. NPK is the chemical abbreviation for nitrogen (N), phosphorus (P), and potash (K). By law, all fertilizers must be labelled with the percentages of NPK in their formulation. Nitrogen is available in many forms, either as a quick release or a slow-release nutrient. Phosphorus is available in quick release form as superphosphate and triple-superphosphate as well as in water-soluble forms. Both rock phosphate

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 and bone meal are excellent organic, slow-acting, long-lasting sources of phosphorous. Composted manures are valuable slow-release nitrogen sources but must be fully composted to prevent burning. Compost and leaf mold are the most value alp soil amendments for providing a slow-release, natural source of nutrients and microorganisms.

Readily available in the U.S. and elsewhere are excellent formulations of water soluble fertilizers with high phosphorus content. These fertilizers are faster acting being immediately available to the plant, and may be applied to the soil or as a foliar feed. Water soluble, chelated trace elements (minerals) are most useful in correcting minor nutrient deficiencies.

When using granular fertilizers it is best to water plants thoroughly before applying the fertiizer and then water again lightly to insure that the fertilizer is moved down into the medium where it can be utilized by the roots.

Fish emulsion and other organic plant foods, whether derived from sludge, seaweed, earthworm castings, guano, etc. will benefit your plants tremendously if used sparingly on a regular basis. Magnesium sulfate (Epsom salts), helps the greening process and lowers soil pH, as azalea growers have long known. Magnesium is the central core of the chlorophyll molecule and is a resonator for the photosynthetic process. Magnesium sulfate will help prevent leaf scorch and, if used as a foliar feed, will be faster acting and more effective than iron.

Controlled-release or time-release fertilizers are beneficial in providing sustained release of nutrients over a given time frame, but most are balanced formulations such as 13-13-13, or high nitrogen blends such as 18-6-12, and are therefore not recommended for plumerias.

In tropical areas where manures and oil cake residues are easily available and very inexpensive, gardeners often make manure "teas" and oilcake paste. A weekly application of groundnut (peanut) oil cake made into a paste and spread evenly over the top of the pot then watered in, will promote larger flowers and more abundant inflorescences. To make oil cake paste, soak an equal amount of oil cake and water for six hours. This will render a thin paste and soaking for six hours will not produce a bad odor. Manure "tea" is made by soaking one part manure in three parts water and then straining off the liquid, diluting it to a desired strength and applying it to the plant and watering lightly.

With all fertilizers, a good general rule to follow is to apply light applications of fertilizer frequently rather than heavy doses at longer intervals. We learned a secret from orchid growers in Thailand that has enabled them to double and triple their cutflower production. Instead of fertilizing with a tablespoon of fertilizer per gallon every two weeks, they dilute the amount to 1/14 and fertilize every day. Their procedure is to fertilize in the morning and then water in the afternoon. This washes off any salts that may accumulate on the plant while the fertilizer has already been absorbed!

After studying the nutritional requirements for plumerias for 20 years, we have recently formulated a fertilizer that meets all their needs, whether in containers or in the ground. This is a supplemental fertilizer in granular form that should be applied every 7 to 10 days, from the beginning of the growing season in spring until 1 or 2 months before the first frost date. It contains many of the ingredients listed in this chapter in the ratios we have found to be most beneficial.

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There seem to be two entirely opposite experiences in growing plumerias in containers that should be noted. Some growers insist that their plants will not bloom until they are completely rootbound. Others are certain that plumerias do not like to be  rootbound and must be potted in larger containers or removed from their containers each year to have their roots trimmed and then repotted. After examining the evidence on both sides, we offer the suggestion that perhaps the question is not so much whether the plants are rootbound or not, but how much nutrition is being supplied.

Proper fertilizing is the key to successful flowering. Be generous in feeding your plurnerias, feed them regularly and experiment with top-dressing if you cannot or do not wish to root prune your plants. The more care you take in feeding, the greater the rewards in flower production and overall vigor.

 

MULCHING

 

The importance of mulching cannot be overemphasized. The many benefits to be derived from proper mulching include: moderating soil temperatures, weed suppression, moisture retention, the building up of organic matter and aesthetic enhancement. When mulch is properly applied it will even inhibit the spread of soil-borne diseases by preventing soil from splashing onto the leaves. If you plant in the ground, by all means mulch. Even if you garden only in containers, mulching will help prevent excessive evaporation and heat stress by providing an insulating blanket between sensitive feeder roots and the sun's rays.

 

PRUNING

 

Plumerias rarely need pruning since they have basically symmetrical growth with- out problems of crossing branches or dead limbs. Still, there are valid reasons for pruning. Many plumerias, especially seedlings, will produce rapid vertical growth without a balance of horizontal growth, bearing their flowers at too great a height to be appreciated and creating problems of unwieldiness when the time comes for winter storage.

There are no great secrets to pruning plumerias. They can be safely cut at any time of the year as the drying latex will heal the wound quickly. Be sure to cut just above a node and at a slight angle. Plumeria nodes are fairly close together so this should not present a problem. At least one and as many as three or more branches will emerge from the latent buds beneath the cut. Observing the direction of the bud will enable you to control the direction of the terminal and lateral branches. Some sources recommend treating the cuts with asphalt tree paint. In areas of frequent rainfall this may have some validity but we have always found healing to be so rapid that this

treatment is unnecessary.

Do not hesitate to prune to create better branched plants that will produce flowers at a desired height. Plumerias will branch rapidly after pruning and in tropical areas

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will even resume flowering in a few months. Dave Emison, of Houston, has shared some of his experiences in pruning Plumeria obtusa with us. Dave was hesitant to prune his plants and like other devoted plumeria growers found it to be a traumatic (for him, not the plant!) experience at first. But when his 'Singapores' grew too tall and became unmanageable, Dave finally resorted to pruning. His purpose was to create denser, more compact plants, to reduce height so the flowers could be viewed more comfortably and to enable the plants to be handled more easily. Dave envisioned the best place to make a cut so that the resulting growth would fill in the plant most aesthetically. On 'Singapore', he usually had three branches form immediately beneath the cut. His plants responded very well and once pruned and structured as Dave wished, he found that most didn't require any severe pruning for at least another three to four years.

One note of caution should be added, however, in pruning plumerias. Remember that plumerias produce flowers from the tips of their branches. In areas with shorter growing seasons than in the tropics, a plant may not have time to develop an inflorescence until the year following the pruning. Also, pruning sometimes causes branches to form at unattractive angles to the main stem. By contrast, branches that are produced at the base of a bloom stalk are always pleasing and symmetrical. You will achieve better results by fertilizing and getting plants to branch as a result of blooming.

 

HYBRIDIZING

 

There comes a time when having successfully grown and flowered plumerias from cuttings and seeds, both in containers and in the ground; having learned the best soil mixes and fertilization schedules; and having achieved the upper hand with insects and diseases, the plumeria enthusiast turns his or her .attention to hybridizing. What if, one says, I could combine this deep red with that prolific, large-flowered white and achieve the best qualities of each? Thus begins, for many, a direction that will become a lifelong preoccupation, attempting to create more and more beautiful, long-lasting and fragrant flowers, aspiring towards perfection.

Let's look briefly at some of the most desirable traits of plumerias and the qualities we would like to develop. Here are some ideas; not necessarily in order of importance:

 

1. Flower substance — Improved substance would enhance the keeping quality of a flower—and who would not like to have a flower that would last many days in perfect condition? Too many of today's seedlings have petals that are thin, easily bruised and fade quickly.

 

2. Intensity of fragrance — We have already distinguished 12 characteristic fragrances; from the scent of coconut oil to many types of citrus; from the smell of ripe peaches to the haunting, heady aroma of jasmine and the unforgettable Frangipani perfume. Through hybridizing we might intensify fragrances and

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possibly create new ones, adding to the range of perfumes we already enjoy from the many plumerias in cultivation today.

 

3. Flower shape and size — This is another fascinating area for exploration and one to which Bill Moragne, in Hawaii, devoted much time. Could one create flowers 7 to 8 inches across with shapes like pinwheels or dinner plates? Why not? A number of cultivars already approach 6 inches and we have read reports of hybrids of similar size in other areas of the tropics. We have grown many that measured 4 to 5 inches and have many yet to introduce from other countries that could form the basis of breeding stock for the future

.

4. Flower color — Endless possibilities abound for new colors and color combinations. This is an exciting field. We have seen some hybrids that border on lavender, some tending toward pure orange, and occasionally a few with variegations that are truly remarkable. We can see the extraordinary work achieved by plant breeders in other fields such as roses, gladiolus, annuals and perennials, and once we begin controlled breeding programs with plumerias, we will be amazed at the results.

 

5. Duration and prolificacy of bloom — Perhaps in the future we will be able to develop plants that will flower abundantly from the first warm weather until the onset of winter, extending our enjoyment immeasurably.

 

6. Size and density of inflorescences — Many inflorescences have sparse blooms or only open a few flowers at a time. Through selective breeding we might increase the size of the inflorescence, the number of flowers open at one time and the density of the flowers in a cluster.

 

7. Plant size and shape — Experiments are already under way at the University of Hawaii's Experimental Station at Waimanolo to produce compact plants with many breaks so that more flowers can be produced per plant for the lei industry. The more growing tips a plant produces, the more flower clusters it can bear. Lei growers are also looking for intensity of color and good substance so that leis will last longer. I'm sure that all of us in non-tropical areas would appreciate low, bushy plants ablaze with color during the growing season and easily handled for winter storage!

Menninger, in Flowering Trees of the World, can easily inspire us to begin hybridizing with the following quotes:

Most Plumeria blossoms are 3 to3^1/2 inches across, but large-flowered types have developed as distantly as Kenya and Hawaii. Jex-Blake (Gardening in East Africa, Ed.4 Longmans, Green & Co. London, 1957) tells of receiving seeds from a friend in Tanganyika who had a very good reddish-orange kind. It had hybridized with the common white, and nearly every plant that resulted produced flowers of different sizes, colors, and even slightly different scent. They

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varied in color from pink to white and lemon-yellow and were almost as large as magnolias.

 

William F. Whitman reports from Honolulu: "On a tree in the Manoa Valley, in a partially shaded location which received full sunlight in the later afternoon, the average size of the larger blooms was six inches across the individual flower."

Albert de LeStang in northern Queensland reported the basal tube crimson, underside of petals golden veined with rose, the edges in and out bright rose, the inside petal whitish tinged golden, the base canary yellow with red centre; all colors fade to pale white, gold and rose as the flower ages. At the flush flowering he considered this variety the loveliest of Plumerias.

We hope we have whetted your appetite enough to venture into the rewarding world of hybridizing. When we first published our Handbook on Plumeria Culture in 1985, we knew of no controlled hybridizing experiments anywhere in the world Since then we have had the special privilege of meeting Mary Moragne Cook and learning of her father's success in hybridizing plumerias. We have devoted an entire chapter in this second edition to his unique work.

 

Pollination

 

Pollination in nature occurs by the action of insects, wind and water. For certain plants there are more propitious times of the day for pollination, when the pod parent is more receptive. Through experience we learn the best time to transfer the pollen from the pollen parent to the seed parent. (With hibiscus in India, we had our best results at about 10:00 a.m.)

The reproductive systems of plants are extremely diverse in form but will contain the following:

Female parts: Pistil — consisting of the stigma, style and ovary.

Male parts: Stamen — consisting of the anthers (recepticles for the pollen) and the filaments (that hold the anthers).

It is more difficult to pollinate plumerias than many other plants such as hibiscus and passion flowers which have reproductive parts that are generally large, visible and accessible. It is exacting work requiring good eyes and a steady hand but you will have all the necessary knowledge after reading this chapter. Even though some plumeria varieties do not bear seeds, all flowers contain both male and female reproductive parts. In the following description of the steps of pollination, we refer to the flower or plant from which the pollen is taken as the "male parent" or "pollen parent" and the flower or plant to which the pollen is transferred as the "female parent" or "seed parent". With "open pollination", only the seed parent is known. Even if we transfer pollen from a pollen parent of our choice, we cannot be certain that this will be the only pollen received by the female parent unless we have first emasculated the anthers from the female to avoid the possibility of self-pollination. The female flower must

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then be covered to be certain that no other pollen is transmitted by insects, etc. Despite the claim by some breeders that mixing pollen on the stigmas of the female parent can lead to wonderful color combinations in new hybrids, nature simply doesn't work this way. Even though pollen from several different male parents may be applied to a stigma, only the single grain whose tube reaches 'the embryo sac first will complete the pollination and all the others do not play a part in the fertilization process.

When we have chosen the seed parent, we must then gain access to the reproductive parts which are hidden deep near the base of the corolla tube. There are various methods of achieving this and we will examine some of them.

An excellent step-by-step description of how to hybridize plumerias is found in Circular 410, entitled Hawaiian Plumerias, by Watson, Chinn, Clay and Brewbaker, issued by the University of Hawaii Cooperative Extension Service (no longer in print):

1. Select in the morning two newly opened flowers, one as seed parent and one as pollen parent.

2. Cut off corolla tube about one-half inch above junction of the tube and the stem. Allow latex to flow from the cut and dry the latex with some absorbent material.

3. Carefully open the corolla tube with a sharp needle to expose the style and some of the surrounding anthers.

4. Remove the anthers to avoid possible self-pollination.

5. With a needle introduce the pollen to the mid-section of the style or within the receptive collar of sticky fluid.

6. Protect the style and reduce drying by slipping a 2-inch piece of large plastic drinking straw over the style and plugging it at the top with wet cotton.

7. Tag the pollinated flower, indicating the parents used — "Sherman (seed) x Rainbow (pollen)" — and the date.

A successful pollination will result in the fertilization of the ovaries, causing 2 seed pods to enlarge within 2 weeks after pollination. In about 7 months these seed pods will be nearly mature and should be covered with a paper bag to prevent the loss of the hybrid seed. The seed pod will split open in from about 8-8^1/2months from the date of pollination.

It will help to:

 

1. Use flowers on trees that are known to have set several seed pods naturally

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. It is preferable that the trees be located where flower picking is controlled.

2. Sterilize pollen applicator with 95 per cent alcohol before pollinating with different pollen to avoid pollen contamination.

3. Label pollinated flowers with bright colored tags and secure them to the "stems" of flowers to record the pollination and to discourage accidental picking.

4. Allow seed pod to open naturally before harvesting seeds.

5. Harvest seeds promptly to protect them from being eaten by insects.

6. Try reversing parents if your first attempt is not successful, since some plumeria flowers are better for seed than for pollen parents.

With this as our starting point, we can consciously begin hybridizing plumerias, assisting Nature in her varied and splendid creations.

 

PESTS AND DISEASES, PROBLEMS AND SOLUTIONS

 

Plumerias are remarkably resistant to insects and diseases. In India we experience 1 no problems whatsoever and in 12 years we never had to spray! Occasionally during times of heavy rainfall, black fungus would appear briefly only to disappear with warm sunny days.

When any plant is introduced into an environment that is markedly different from its natural habitat it may be susceptible to problems not formerly encountered. In Houston we have seen a number of such instances. Plumerias grown in areas where there is insufficient air circulation are often attacked by spider mites. Spider mites can often be washed off with a strong jet of water and are also relatively easy to control with insecticidal soap. Some growers have had success with Malathion even though k is not listed as a specific control.

In Hawaii, we have seen large plantings of plumerias attacked by borers, the larvae of the long-horned beetle. Dr. Criley writes: "Short of spraying weekly and using very toxic chemicals to treat the trees, there is little that can be done." Dr. Criley also mentions that he must prune out dead branches every time he goes over to the trial grounds of the University of Hawaii at Waimanolo. We would like to emphasize that everyone on the mainland U.S. should pay very close attention to their plants and be ever watchful for borers. Plumeria cuttings are being sold in plastic bags at airports and gift shops in Hawaii by a growing number of different companies who may or may not be careful to take cuttings only from "clean" trees. In the early stages, borers can be detected by the presence of tiny, pin-sized holes in the bark from which exudes a small dot of black material. The area soon becomes soft as the borer eats away the inside of the stem. If you find evidence of a borer in a branch, cut the branch back to clean wood and destroy it.

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In his letter of September 14, 1988, Dr. Criley responded to several of our questions as follows: "I asked our extension entomologists about the long-horned beetle, Lagocheirus obsoletus Thorns. There is no extensive published information about it in plumeria that they are aware of. The main mention I am aware of is in Univ. Hawaii Cooperative Extension Circular 410 (Watson, Chinn, Clay and Brewbaker, 1965). Even in this, there is not a straightforward recommendation for control, mentioning only malathion. I do recall one recommendation for the use of the insecticide SEVIN (carbaryl) which would control the insect if it chews on treated tissue and consumes the insecticide. I am not aware of specific recommendations and have done no studies on the problem. The entomologist indicated that it does attack other plants and mentioned having isolated it in some banyans here in Hawaii. Thus, I can't really say when it emerges and lays its eggs, how many instars (stages of development) there are and how long they take, etc. It would be interesting to try biological controls such as the new nematode biologicals which attack various insect grubs and caterpillars, but the main problem is to get them into contact with a grub that has embedded itself inside a branch. It might deserve support by PSA [Plumeria Society of America] to study controls if they would like to make such a grant."

In Circular 410 mentioned above (and quoted elsewhere in our handbook), the authors include a section on "Insects and Diseases" from which we quote two relevant paragraphs: "One insect which has recently caused considerable damage to limbs of old established trees is the grub of the long-horned beetle. These larvae are whitish or yellowish, soft-bodied, and possess powerful mouthparts for biting into the hardest of wood. Wilting of established limbs of the plumeria may indicated the presence of this insect under the bark. If the insects are not present in large numbers, remove the larva by cutting into the bark. Since weakened trees seem to be more prone to attack from these beetles, potential damage may be averted by maintaining the trees in a vigorous condition."

"If insect injury is serious, a regular spraying program may be necessary to main- tain clean and healthy plants."

The authors recommend Malathion and Captan for borers. They also include the following observation: "In Hawaii, disease attributed to bacteria, fungi, and viruses are rarely serious on plumeria trees." They mention scale insects, beetles, and thrips as well as mites and aphids, all of which are not difficult to control with the use of 'insecticidal soap and/or a specifically approved chemical. '

We have mentioned the incidence of sooty mold formation on limbs and trees. This is a black, powdery fungus that is unsightly and grows on the secretions from many of the above-mentioned insects. Again, it is easily controlled by an insecticidal soap or even soapy water applied with a forceful nozzle spray.

A fungus that attacks the growing tips of the plumeria can be quite serious if not controlled in the early stages. If not treated, not only will it destroy any emerging buds but will prevent any further development of the growing tips, eventually killing the plant. If a systemic fungicide (we have had excellent results with Benomy), is applied directly to the infected area, the problem, which seems to occur with high humidity, is rapidly controlled. Bayleton has become available as a granular systemic just this year and should prove efficacious for most fungal problems when applied to the soil and watered in thoroughly.

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In the past five years a "rust" fungus, Coleosporium domingense, which manifests as bright orange pustules on the undersurfaces of plumeria leaves, has appeared on plumerias in Houston gardens. In its initial stages it was easily controlled by Daconil 2787 (active ingredient chlorothalonil), but this was not effective on advanced cases Mr. Larry W. Barnes, the Extension Plant Pathologist of the Texas A & M Agricultural Extension Service and Mr. Rayford G. Kay, Harris County Extension Agent (retired) examined and identified the rust in October, 1984. Their recommendation was Bayleton, a highly effective rust fungicide that is systemic. They wrote further that there was no fungicide currently cleared to be used for rust control on plumerias

Since the above was written we have discovered an article in the Proceedings of the Florida State Horticultural Society. 97:247-248, 1984. The author, R.T. McMillen Jr., has written an excellent article entitled: "Oxycarboxin a New Fungicide for Ccntrol of Frangipani Rust in Nursery and Field". Mr. McMillan's research concludes that "... foliar sprays of oxycarboxin at 1.2 g and 1.7 g per liter effectively controlled rust [Coleosporium dominguense (Burk.) Arth.] of frangipani (Plumeria rubra L.) in nursery and field trials. Oxycarboxin effectively stopped defoliation as well." In discussions with Howard Walters, Director of the Houston Rose Society, and from recent correspondence with Dr. Richard Criley, we have learned that oxycarboxin is the active ingredient of Plantvax and that it is a systemic fungicide effective in controlling rust. Howard says it is the best fungicide he has found for the control of rust on roses and grapes. Also, it is a low concentration material and safe for the user. one application will suffice for roses with no leaf damage. Plantvax-75W is readily available in the U.S. and is used extensively by rose growers in California.

We quote further from Mr. McMillan's research: "Oxycarboxin (Plantvax-75W) is a wettable powder suitable for use as a spray when suspended in water. . . . Frangipani rust is an annual problem for nurseries and home owners in South Florida and the Caribbean region. The disease reduces the saleability of nursery stock and the aesthetic beauty of a full foliage flowering plant. The use of oxycarboxin not on y reduces the disease but has an obvious advantage over the other recommended fungicides [Dr. McMillan tested mancozeb, ferbam, and sulphur as well] since it only takes 4 applications as compared to 8 or more weekly sprays with presently used chemicals Oxycarboxin as a soil drench might be [as] effective as the foliar sprays but such evaIuation has not been made." Lastly, Dr. McMillan writes: "There were no toxic effects observed on the leaves, flowers or stems with oxycarboxin at the test rates and spray frequencies evaluated. At present oxycarboxin is approved by Environmental Protection Agency (EPA) for use on ornamentals and is available on the market."

When spraying for rust remember to treat the upper surface of the leaves where the

fungus begins, as well as the lower surface.

Having grown thousands of seedlings, Elizabeth Thornton cautions against the fungus gnat whose invisible larvae feed on the tender new roots of plumeria seedling . We quote her recommendations for control: "An application of 5% Sevin dust

watered in or 5% liquid Sevin used every three weeks will eliminate this pest. Continue treatment until no gnats are seen flying. Avoid getting Sevin dust on the leaves as leaf burn can occur."

Sunburn often appears on the stems of plumerias when rooted cuttings have been transplanted and moved into full sun after weeks or months in filtered light or light

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shade conditions. The result is a bit unsightly but we have never seen plants adversely affected. Leaves can also exhibit signs of scorching. There are a number of potential causes: watering in the heat of the day when water droplets can magnify the sun's rays; the combination of intense sun and air pollution (causing yellowing and dropping of leaves); watering with tap water containing excessive salts; fertilizing with products having a high salt index. It is interesting to note that plumerias will grow under very difficult seaside conditions and, though often showing salt and wind burn on the leaves, will continue to grow and bloom. With sufficient organic matter added to beach sand, we have seen them adapt to planting on the beach only 50 feet from the water.

Stem rot is usually due to an excess amount of moisture when rooting cuttings or to moisture combined with cold temperatures during winter storage. It may also be due to overwatering or poor soil that retains too much moisture. Careful watering and close attention to the moisture holding capacity of the growing medium are the best ways to avoid the problem. Once stem rot begins it moves very quickly. If you cut back to solid material (no brown showing) you can often save the remaining portion of the plant. It is a good idea to dust this with dusting sulphur or a fungicide.

Although we have attempted be be as thorough as possible in defining the potential problems and solutions concerning plumeria pests and diseases, we stress once again that plumerias are exceptionally resistant to both. By maintaining healthy plants, observing them carefully and treating potential problems in the early stages, one will find that plumerias are among the world's toughest and most resistant species, rewarding us with untold wealth and beauty with a minimum of care.

 

DORMANCY

 

All the plumeria species and cultivars we have studied, with the exception of P. obtusa and some of its varieties and cultivars, have a dormant period (1 to 3 months, according to climate zones) in which they cease growth and flowering, usually shedding their leaves, as they store energy for the next season. This dormancy extends from the onset of cooler weather in the late fall to the first warm days of spring when the plant will once again initiate growth.

Some variations in this cycle should be noted. Many seedlings will go through their first and often second years without shedding their leaves. One may even find that in a group of mature plants of about the same age and growing under the same cultural and climatic conditions, some will shed their leaves while others will hold them throughout the winter and continue growth again in the spring.

Climate is not necessarily a factor in either the retention or shedding of leaves. In the tropics, especially in areas such as South India, where the temperature on a "cold", windy night in January might plummet to 68 degrees farenheit, most plumerias still drop their leaves. Another interesting phenomena is that the evergreen species, P. obtusa, also sheds its leaves for a brief period every 2 or 3 years.

During dormancy, plumerias do not require water since they are not producing flowers or leaves. In fact, excessive watering in the dormant months of winter usually leads to stem rot. Occasionally a plumeria will initiate an inflorescence late in the season

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 just before the onset of cold weather. We have observed that it will begin to elongate and then discontinue growth. Many times it will drop during the winter, but we have seen a number of them remain on dormant plants and flower in the spring.

Plants that "are placed in a sunny window and allowed to continue growing during the winter should be watered sparingly, about the same as other tropical foliage houseplants during cold weather. Fertilizing should be discontinued during this time as uptake of nutrients is slowed considerably. Given proper culture, we have seen evergreen varieties in full bloom in the home in December!

As mentioned above, dormancy varies somewhat according to climate. Some of our trees at the Matrimandir Gardens were deciduous for no more than 2 week:,. Others dropped their leaves for about 6 weeks. In temperate and sub-tropical climates dormancy often extends to 3 or 4 months. In Hawaii, trees are deciduous from late December through February, and in California for about 4 months. An interesting note on mature trees; a friend in Pondicherry, South India, has studied plumerias for years and has noted that mature trees of P. rubra forma acutifolia (25 years and older) drop their leaves with the onset of the monsoon (late October and early November) for 6 to 8 weeks. A definitive study should be conducted on dormancy in plumerias and the effects of day-length and temperature fluctuations on species and cultivars.

 

COLD TOLERANCE

 

Although plumerias must be considered tropicals and cultivated as such, especially in temperate areas, there are encouraging signs of greater cold tolerance exhibited in some cultivars in southern California. Since plumerias are frequently planted in t he ground in these areas, it would be a valuable study to determine which cultivars are the most cold tolerant. This information could extend the outdoor growing season in

much of the southern U.S.

For now, thanks to our many correspondents, we have a few items of interest to report. From plumeria growers in California we are informed that P. obtusa ('Singapore') is the least cold tolerant of all and can only be grown successfully in the ground in the mildest coastal areas. Among cultivars that have shown somewhat greater cold tolerance are 'Plastic Pink' and 'Celadine'; among the most cold hardy are 'Candy Stripe', 'Dean Conklin', 'Kaneohe Sunburst', 'Mela Matson', 'Scott Pratt', and sa- moan Fluff. 'Irma Bryan' has also survived light frosts with only the growing tips showing damage.

An interesting note concerning cold tolerance comes from a friend in California who has planted plumerias as a large hedge around the border of her yard. She has observed that occasional freezes (28 to 30 degrees F.) lasting only an hour or two will turn the tips of her plants black. The tips then die back about 3 or 4 inches, she breaks off the blackened area, and in the spring the plants produce from 1 to 5 new growing tips just below the break.

We should note once again that discontinuing the use of fertilizer in late summer will enable plants to harden off and reduce the susceptibility of tender growth to freeze damage. There is some evidence that applications of potassium during the growing season tend to build starch reserves in the trunks and limbs of trees and con tribute

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¦ to greater cold tolerance, but we have no confirmed data on this regarding plumerias. It has been noted, however, that plumerias will develop greater cold hardiness with age.

 

OVERWINTERING

 

Two major problems concerning winter protection for tropical plants are well known. The first is finding a place for them and the second is getting them into place! Plumerias are an additional challenge, especially older plants that have gained considerable height and spread. The problem of winter storage is also compounded for many plumeria afficionados who may have as many as 50 or 60 plants. (We know a few who have to find a place to store hundreds!)

Plumeria growers have long followed the standard practice of bringing plants into greenhouses and keeping the temperature as high as economically feasible, or into the house and trying to solve the logistics nightmare of finding enough sunny windows.

In the early 1980's, the late Frank Tuxworth and a few intrepid plumeria growers in Houston (where a light freeze or two each year is seemingly inevitable, and occasionally a "Blue Norther" will send temperatures into the teens), decided to experiment with overwintering techniques. These courageous and innovative individuals removed their plants from the containers, carefully shaking the soil off the roots, wrapped them in burlap or newspaper, and stored them in a closet, spare bedroom or warm attic. In the spring they brought their plants out after danger of frost was past, repotted them in fresh, well-drained, fertile soil and watched them burst into leaf and bloom!

The technique they discovered is entirely safe since plumerias have a marked dormancy. Plants that are left in their pots need no water at all while they are in storage as long as the plant is well established and has a good root system. It seems to matter little whether some or all of the soil is removed, whether plants are kept in darkness or receive a little light, whether the leaves are removed or left on (they'll drop off anyway), or what is used to wrap them, as long as they are kept above 40 degrees F.

During the past few years we have experimented with storing plants of all sizes and have found that perfectly healthy and well-rooted cuttings — but ones that had not rooted until late in the summer in community pots — tended to develop stem rot which often travels through the entire container. For this reason we recommend that they be transplanted into individual pots and kept growing during the first winter. Watering can be cut back considerably but not withheld altogether.

If you have many plants to store and not much space, we would suggest the following  as the safest procedure to use:

Wait until the temperature starts dropping into the upper 40's. Allow plants to dry thoroughly before removing them from their containers and shake off enough soil to facilitate handling and transporting. Cover the roots with newspaper or wrapping paper and secure with twine. If you remove the leaves the plants will Pack more tightly and you avoid having to clean up dead leaves in the spring. (It is best to remove the leaves a day or so before packing so the latex will dry thoroughly.) Store where temperatures will remain well above freezing and bring plants

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out again in the spring when nighttime temperatures are no longer dropping below 40 degrees F.. Do not be concerned if plants show some dessication or shriveling of their branches; they will rapidly fill out once watering and growth is resumed.

Even though it sounds drastic, the success rate with this technique of overwintering has been phenomenal. The only drawback we have noticed with the soilless storage method is that flowering tends to be somewhat delayed in the spring. If you ha /e only a few plants, we recommend keeping them in their containers, but following the other proceedures outlined above. Both ways are not only convenient and practical but enable us to increase our collection of plumerias and therefore our enjoyment of more numerous colors and forms.

 

Removing Plants from the Ground for Winter Storage

 

In warmer sections of the U.S. there are a number of advantages to planting directly in the ground as discussed in the chapter on Planting and Transplanting Removing plants from the ground is not a very difficult task. The mass of plumeria roots is rather modest compared to the amount of top growth plants can develop in a season. We have successfully transplanted fully grown trees more than 12 feet in height and 15 feet across and have never lost one. The following directions may be used as a general guide to transplanting most plants:

1. Dig only when soil moisture is sufficient to hold a ball together

 2. Use a sharp spade (or sharpshooter) with straight sides.

3. Dig in a circle around the trunk — a 1 foot radius will give you a 2 foot ball which should be sufficient for all but extremely large trees.

4. Dig straight down all around the tree. Do not pry up.

5. Make a second line of cuts outside the first on an angle towards the trunk co meet the bottom of the first cuts. Then undercut as deeply as possible towards the trunk.

6. This should loosen the ball completely and preserve the maximum number of roots.

7. It is best to work with another person (husbands and wives take note!) to remove the ball from the hole as this is physically taxing work and 2 additional hands will also help keep the ball intact.

8. If you wish to keep some soil around the roots yet reduce the size of the ball ,it is easy to shave it once you have it out of the ground.

9. If you would like to bare root your plant you can either wash the soil off with water, gently loosen it with fingers or cultivator, or shake steadily and firmly.

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GROWING PLUMERIAS INDOORS AND UNDER LIGHTS

 

As mentioned in the beginning of our handbook, people as far north as Canada ire flowering plumerias indoors. Give them a sunny location for enough hours of the [ay and plumerias will flower easily providing their other requirements such as watering and fertilizing are met.

For information on growing and flowering plumerias under lights we quote from letters by Jerry A. Neyman in Denver, Colorado, and George F. Slusser in Woodinville, Washington. George writes that his ". . . eight year old plumeria does not lose its eaves in winter when the temperature does not drop below 60 degrees F., either in a south window or under fluorescent lights. I kept this plant dry and under fluorescent lights and it appears to be more vigorous this spring by producing more leaves per length of the stem." `

Jerry has written a very detailed account of his experiences in growing and flowering plumerias under fluorescent 'Grow Lights', valuable information that we are pleased to share. We would like to note that he also sent us a photo of one of his plumerias in full bloom under lights! Jerry achieved his initial flowering in March 1986, from an unnamed yellow. The plant was 12 inches high and planted in a 6 inch pot. In a 48 inch shop-light fixture he put two 40 w. GE 'Wide Spectrum' bulbs. He placed the plant in the center of the bulbs, at a distance of 8 inches and gave the plant 16V2 lours of light, fertilizing with V-t strength 15-30-15 every watering. Humidity was kept at 70% using a cool mist humidifier as the source. Temperature was kept at 75 to 78 degrees during the day and 60-65 degrees at night. In June 1986, Jerry wrote: ". . . one plumeria plant (above) is under fluorescent grow lights. Plant grows steadily, without any growth problems, leaves are medium to light green in color, 8-10 inches in length, and a crispy hardness. It has been my observation that this 'hardness' of leaves indicates favorable growing conditions, especially light requirements are a prerequisite for flowering."

In December 1987, Jerry placed a plant of 'Kimo' and another unnamed yellow under a new light source, a 2 foot x 4 foot five-bulb light fixture, using four 'Gro-Lux' and one 'Cool White' bulb. This time he kept the humidity a bit higher, 75 to 80%, and the day temperature from 80-82 degrees with night temperatures averaging 70 to 75 degrees. He also kept two 6-inch fans on either side of the room to provide air movement. Both plants were in small pots, 5 and 6 inches respectively. This time he fertilized with high phosphorous fertilizers, BR 61 and Super Bloom, at ^1/4 strength, alternating with each watering.

Again, we quote his most interesting conclusions: "It has been my observation that plumerias will grow much faster and initiate the flowering process under a higher light intensity. Light intensity is the key, the most important factor in the proper growth and flowering of plumerias under 'Gro-Lights'". (Note: This corresponds exactly with Dr. Criley's experience using the silver shield to increase light intensity.) Jerry continues: "With the correct light intensity, regular feedings and favorable growing conditions, it will take approximately 31/2 to 4 mos. for initiation of flower bud set."

Within 4 months Jerry had both plants developing flower buds and all this took place in his basement!

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