Plumeria

(Question)

My plumeria is in it’s 1st year and I kept indoors from March through May. It had started to put out leaves and did well. I put it outdoors in the full sun and watered and fertilized. It grew and developed lots of leaves. But in the last 2 weeks it appears to have disease which I think is powdery mildew. I have literally been dousing it with an appropriate fungicide. It has holes in some leaves and has dropped 2 larger leaves.
What do I do now as I plan to overwinter it inside. Assume leaves will drop off and I won’t water it. But do I bring it inside by the end of Sept when temp. starts to drop?
I am in Toronto.

(Answer)

Plumeria should be planted in a well-drained, slightly acidic potting mix, such as that produced for cacti. In southern Ontario, they are not hardy and need to be brought inside for the winter,  so it is best to keep them in a pot. In the warm weather, the pot should be placed outside in full sun and given at least 1″ of water per week. The exact amount of moisture needed will depend on the size of the pot and how hot the weather is. The soil should not be continuously wet. Fertilize at the beginning of the growing season in the spring and again in the early fall with a high phosphorus plant food. Mealybugs, whiteflies and spider mites are the usual insect pests that bother plumeria. Topically applying insecticidal soap or horticultural oil will keep the insect populations down.

When night time temperatures fall below 10 deg C, you should consider bringing them inside. They should be kept near windows or in the basement under lights (16 hours of light). As their growth slows, reduce watering drastically to prevent root rot and don’t fertilize. To reduce the mess when they drop their leaves, you could remove up to 3/4 of the leaves manually when you bring them in. Cut at the end of the petiole, leaving the petiole attached to the branch/trunk. This way they will bleed less white sap.

The following is a good YouTube video on overwintering plumeria in a cold climate:

I have tried growing plumeria myself and find them challenging, partly because they grow so slowly. I gave up before there was any flowers. When I was in Hawaii, a book sold everywhere was: How to Grow Plumeria Anywhere in the World. Maybe you can get it from the library. Good luck!