First of all, do not be concerned that these cultural instructions appear to instruct that plumerias require too much fuss. They do not. I only have attempted to include the most detailed and concise information to satisfy those perfectionists who want to give the best possible care to their plumerias. Once established, plumerias can survive on much less care than most plants, although for optimum flowering they should receive regular water and higher phosphorus fertilizer.
Most plumerias are a true tropical flowering tree and all will freeze if exposed to temperatures below 33 degrees F.
Dwarf plumerias have a habit of growth much smaller than a tree and are more suitable for patio, deck, balcony or indoor specimens.
When day high temperatures stay under say 95 degrees F, dwarf plumerias prefer full sun as many hours as possible. When day high temperatures consistently climb above 97 to 98 degrees F dwarf plumerias should be moved to a location where they only receive morning sun till perhaps 1 or 2 o'clock, then the remainder of the afternoon shadecloth filtered sun only, or just shade. Plumerias must receive at least 6 hours of direct sunlight each day in order to flower well.
Soil or growing media
Plumerias in their native tropical environment grow in natural soil. Most of us must grow our plumerias in containers so that the plants may be more easily transported to protected storage during wintertime. Plants in containers do not have the benefit of "capillarity" which is usually established in natural earth soils and assists in drainage. Therefore, for best results with container growing of plants horticulturalists use special potting mixtures instead of soil. In order to accelerate growth and provide further insurance against "wet feet" on the roots I use a special custom growing media with beneficial EPA registered microbes included for container culture which is available for purchase here. I do not recommend planting plumerias in containers using common soil. I repot my plumerias to larger pots usually in the 1st of June once they are showing they are well "root bound". If planting in a clay pot I recommend you line the pot with a plastic trash bag, but be certain to cut the bottom of the bag off for proper drainage. After planting just run the scissors around the edge of the pot cutting off excess plastic. This will prevent the clay pot from "wicking" moisture out of the pot so rapidly during hot summer days.
Pests
Occassionally aphids may attack, but I usually ignore them. Spraying the undersides of the leaves with a spray nozzle on a water hose usually dislodges most pests who reside there.
Rarely, the longhorn beetle may attack plumerias. This insect bores into the stem and lays eggs inside. The eggs hatch and larvae emerge to feed. Look for obvious damage to the stems. Some growers cut open the stem searching for the insect to crush the larvae. Others use medical syringes (no needle) to inject dilute solutions of liquid Sevin to poison the insect. In 9 years I have never experienced this pest.
A fungus called orange rust may occur on the undersides of the leaves. Isolate the infected plants and cut off all their leaves. Dispose of these leaves carefully in the trash. Do not leave a single infected leaf in your yard. I have had one occurence in 9 years. I sprayed with both the upper and lower leaf surfaces with a fungicide called Plantvax, then carefully disposed of all the fallen eaves and never had another attack.
One other rare fungus is the black tip fungus, which attacks the tips or growing points. We have heard of growers using Bayleton fungicide to control this fungus. It seems most fungus problems occur in coastal climates where the humidity is higher.
For those who like to spray & prefer to prevent problems before they escalate I recommend regular sprayings with Organica Neem Oil and Insecticidal Soap Spray (both undersides and tops of leaves). Only spray after the sun has gone down or in the early morning. Neem oil has also been found to have some activity towards preventing fungus. Contact them at 800-571-3009 to find a local distributor.
Fertilizers
A fertilizer with a high phosphorus (middle number) is the key to encouraging plumerias to bloom well. Also make certain the fertilizer you choose has low nitrogen (first number) to discourage excessive stem elongation, legginess and soft growth. I use special custom fertilizers which I have developed over 9 years of growing and they are available for sale here. These custom fertlizers produce fairly amazing results when used on dwarf plumerias and may be used to obtain similar results on almost all plants. Epsom salts (magnesium sulfate) is applied during the growing season to assist in preventing yellowing and sun leaf scorching of leaves - especially from high summer temperatures.
Watering
When you receive your new plumeria cuttings from me the best idea is that if you do order the special potting mix with the cuttings, upon receipt, take the bags of potting mix and pour them into a large clean bucket. Flood the bucket with about the same amount of water as the volume of potting mix, stir it well, then allow it to stand overnight. If properly done it will look like a very "soupy" mixture. The next morning the potting mixture will have absorbed enough water and be ready to use. Just drain off any excess water.
When you receive your new rooted plumeria cuttings from me, I suggest you pot the cutting in a one gallon or equivalent sized pot. Using a clay pot will add weight and stabilize the cutting from any "tip overs". One gallon plastic pots seem to have too narrow a base, and tip over too easily. I often use the large one or two gallon metal vegetable cans that cafeterias dispose of because they have a wide, stable base. I use a pointed tip can opener to punch several drain holes in the cans.
IMPORTANT: After potting up your plumeria cuttings be sure to water the cutting in well. I suggest you use just a tiny bit of fertilizer in this watering. I suggest using a watering can with a spout that has many tiny holes so it won't just wash all the soil out of the pot. After this watering do NOT water your new plant again until the soil has dried out. Check by inserting your clean finger into the soil 2 or 3 inches deep and feel for moisture. When you do choose a day to water be certain you apply at least about 16 ozs. or 1/2 liter of water at several intervals - like at least 16 ozs.of water every 15 minutes (three times total) over a 45 minute period to insure the potting mix for a 1 gallon sized pot is thoroughly wetted. Repeat this cycle of watering only when the soil has dried out. Perform this watering technique for several watering cycles, at least until the new cutting is showing new leaf growth. Only once the plumeria is established and showing new leaf growth should you water it more regularly.
Water quality - While plumerias are fairly tolerant of most well water, the types of minerals and the alkalinity or acidity of your water supply can sometimes slightly reduce the growth of your plumerias. In extreme cases, heavily mineralized well water can disturb the nutrient balance and cause deficiencies in most all plants.
Check with your local water utility to see if the water in your district is derived from wells or from a surface source such as a lake or river. If you are really interested ask the water utility to mail you a photocopy of a water analysis from the lab they use, then mail a copy to me and I can advise you. Surface water is generally better for all plants and will probably give you a slight edge with your plumerias. If you discover your water supply is from a well your plumerias will usually still grow just fine, just not as optimum as by using less saline or less mineralized water. Here is another alternative. I place a clean 5 gallon paint bucket under the air conditioner drain pipe outside my house and collect this water constantly for watering all my plants. This water is almost like distilled water, so it is almost totally free of harmful minerals to plants such as sodium, or excess bicarbonate.
When day temperatures are below about 80 degrees F you should hold back watering plumerias. Check and make certain the soil has become dry from the last watering. When days become consistently warm above about 80 degrees F with lots of sunny days you can begin to water your plumerias more often if you desire faster growth and more flowering, perhaps every 2nd day, as long as the soil has dried somewhat from the previous watering. I find this technique safer for beginners to avoid problems with possible root rot.
Repotting
Under ideal conditions you may repot your dwarf plumerias to larger pots each year. I suggest repotting from a 1 gallon to a 3 gallon pot the 2nd year, then perhaps to a 5 gallon pot the 3rd year. You can maintain your plumeria in the 5 gallon pot many years, or if size is not a problem repot to a 10 or 15 gallon pot the 4th year.
When repotting I always check the bottom of the pot for any roots growing outside and cut those off. Then, I spread the fingers of my hand and insert my hand over the top of the potting mixture with main plumeria stem inserted between middle fingers then carefully turn the pot upside down and gently knock the pot edge on a step or edge of the deck to loosen the plant. If done properly the root ball should pop right out of the old pot. NEVER handle a dwarf plumeria from the main stem, always handle the plant by grabbing the sides of the root ball. Be certain to repot your dwarf plumeria in it's new pot so the top level of the old potting mix can still be seen, up almost at the top level of the new pot. About 1 inch "freeboard" space is left in the top area new pot for holding water when you water the plant.
A season by season primer:
In the spring when night temperatures climb above 50 degrees F, you can bring your plumeria out of storage and "encourage" it to come out of dormancy. Sometimes there will be some root loss and drying out of branches but do not be alarmed. This a a great time to repot. I would strongly suggest you hold back on watering until your plumeria starts showing signs of new leaf growth appearing. You may fertilize sparingly. Once your plumeria shows an abudance of new growth and day temperatures are at or above 80 degrees F you may start to water and fertilize more generously.
In the summer fertlize and water often. Be certain your plumeria is receiving at least 6 hours daily sunlight for optimum flower production. As the days become shorter in August and September some lower leaf yellowing and leaf drop is normal.
Under ideal weather many plumerias will continue blooming into the fall, in the Southern US as late as November and December. Be careful though, as an early frost can damge or kill your plumeria.
In the fall season stop fertilizing and slow down watering so that the plumeria will be encouraged to go into it's normal dormant period. When temperatures are forecast to fall into the 30's, the plumeria should be protected. Many varieties can be damaged or even killed by temperatures in the low 30's, even if for just a few hours. Better safe than sorry to go ahead and store your plumeria in a closet or space where the temperatures are maintained and it will not freeze and nothing will be stacked on it which will break the brittle stems. A cool greenhouse is not recommended for Plumeria storage.
In the winter season plumerias require very little care - more accurately just storage. But before storing be certain you defoliate (cut off the leaves). The dwarf deciduous white flowered variety will drop all it's leaves every winter whether you defoliate or allow the plumeria to do this by itself. The dwarf evergreen pink Singapore flowered variety is a true evergreen, but will only keep most it's leaves well if it is allowed sunlight during the entire year - a difficult proposition for most homeowners.Some folks suggest not watering plumeria at all during the winter season, however, you may notice some branches begin to dry and shrivel (dessication), so you may want to apply water sparingly perhaps once a month. Plumerias with leaves removed take up much less space than a plant in full leaf, so it's possible to stack them carefully 2 and 3 high on the rims of the pots.