We've all been there: you have a gorgeous plumeria which it flowers like gangbusters through September and October. By Thanksgiving, it has dropped its leaves and gone into dormancy. Then the spring comes, and you wait for signs of life, only to have none forthcoming. Maybe it turns to mush under your fingers; maybe the tiny red claws at the tips start to leaf out, then turn black and never come out again. Here's some information to help you through the process:
We asked a number of our experts how they care for their plumerias before and during the winter months.
Frost cloth needs to be draped completely over the plant. It provides added warmth both during the night and during the day - a greenhouse-like atmosphere. Due to the added warmth during the day, plants handle the cold better at night and come out of dormancy sooner in the spring.
In September, October and November, I add Dyna-Gro Pro-Tekt to the water when watering the plants. It is a silicon solution with potassium. Its function is to "improve heat and drought tolerance; increase resistance to environmental stress; and enhance growth for stronger, hardier plants."
We remove most of the leaves off the parent trees and large potted plants due to the Santa Ana winds in the fall. I hate branches breaking. I also compost all the parent plants in the ground and repot root-bound plants that are in pots. This year I'm trying to fertilize and compost as many plants as I can to see how they do next year come spring. I'm fortunate where I have my plumerias because I have a great south-facing piece of property with little to no frost. I stop watering on a routine basis when the nights start getting cold and the leaves fall off the trees. I make sure there is good drainage everywhere and water doesn't collect at any one place.
A last bit of Sul-Po-Mag on each tree, if possible an extra shot of potassium from bananas or a slow release fertilizer. The potassium really helps with the inner cell strength of the plant and will help repeal any cold weather. My biggest worry this time of year is sunburn. The sun is lower in the sky and generally starts hitting the tree trunk, also the tree has fewer leaves to protect the trunk, so I look for ways to provide shade on days of extreme heat, extreme sun. November and December are our sunniest months in San Diego and unless you have canopy (big trees) it can be difficult to provide cover. Also it's time to cut back on the water, so the tree is even more vulnerable to sunburn. I'll also go through the grove and turn down sprinklers, some I'll cap and won't turn back on until St. Patrick's Day. St. Patty's Day is my annual wake-up party, that's when every tree gets another shot of Sul-Po-Mag and a shot of nitrogen to help waking up.
The only thing we do is to bring our potted plants under cover so that they don't get a lot of extra rain water. This year we bought a small shelter to put the one-gallon pots in to for protection. Those going into the shelter will get their leaves removed. All potted plants will get their last feeding at the end of October, along with some Epsom Salts.
The plants in pots are moved into a structure made of shade cloth. I keep them as close as possible to each other to conserve heat and protect one another. We also run fans close to the ground to keep the air moving. I spray all plants, pots (bottoms too) and soil with Malathion. This also helps control any insects that like to over-winter on the plants. If insect problems do occur later on, I use a spray of Horticultural Oil. Follow all label instructions.
We have a room under our house that is dark and has no extremes of temperature. If we have any cuttings I have large containers that are 18 inches deep. Clean cuttings thoroughly to avoid any insect problems. I put a mixture of #1 Perlite, large chunks 20%, and coir 80%, 20/80, in the bottom 6 inches. The cut ends of the cuttings are placed on top of the mixture. I do not put them into the mix. By placing them on top of the mixture the roots are easy to work with. When I am ready to plant them most of them will have started to put out some roots. I will occasionally mist them with a hand-held spray bottle. If you get them too wet they will rot.
We have never done anything for our plants in the ground - a survival of the fittest environment. (Aside: The best protection is a large, well-established plant in the ground. That's why I don't like to plant anything in the ground past mid-July or so and only after it has filled a 5-gallon pot.) I have lost a few plants in the past; though I discovered those varieties are not very cold-tolerant. I will typically lose some branches over the winter to rot. I inspect them every few days so that I can cut the rotted branches before it spreads through the plant.
Last year in mid-November I fed the plants a mix of Seaweed Extract, Physan-20, and Epsom Salts. Those products are supposed to help protect the plants from the cold. All I know is that in 2014 I didn't lose one branch for the first time ever. Some are concerned with fertilizing so late in the season, as new growth is more susceptible to cold weather. But I know of other growers who have done this for a long time with good results.
As for my pots, I put them in my greenhouses, which are not insulated and are unheated. (I refuse to pay SDG&E any more money than I already do!) So they are basically in there for protection from frost settling on them. And it works well for that, but there are other dangers. For instance, occasional hot spells in March and April can cause sunburn or rot in a hot greenhouse. I use a sun shade and open the greenhouse to keep internal temps down. Running fans in the greenhouses also keeps air circulating and temps down.
For my bag-rooted cuttings, they go in the greenhouse on heating mats on a table covered with wool blankets for insulation.
If you live in the coastal region, you can bring your plant under a patio or porch cover for the winter and it should be fine. In areas of the county that receive frost, you need to take more steps to protect your plant.
Frost damage can cause branch dieback, with branches basically turning to mush. If you cut into the branch, you will generally find a black or brown goo. To save any of the tree, you'll need to cut down until you reach a healthy white interior. It might be best to wait until frosty weather is over before cutting the tree, to reduce the possibility of more damage and having open "wounds" on the tree.
I live in Jamul in the east county, so protecting my Plumeria collection from cold is an issue I deal with every year. I start my protection process by stopping all fertilizer in September. This stops new tender growth from forming very late in the season, which would be more susceptible to damage in the winter.
In mid-December I move all my first-year cuttings and seedlings into my home. As many other potted plants as possible go into the greenhouse (which is unheated). I place several buckets of water amongst the plants in the greenhouse. The water heats up during sunny days and that heat is dispersed at night to help keep temperatures inside the greenhouse tolerable for plants.
The bulk of my collection is in pots and can easily be moved under a porch, eaves, or awnings; this protects them from rain and frost as the overhead covering acts as a barrier to the night sky. The plants are as close to the house as possible. My house is a stucco/brick combo and retains heat that is dispersed at night, which also helps keep the temps up a bit.
I have thirty-eight trees in the ground that I choose not to dig up. Some people dig theirs up every year and store them bare-root style in garages, spare rooms, in rafters, etc. - always keeping them off cold cement - then replant them in spring. This method seems popular in Texas. My in-ground trees receive rainwater during the winter, not much I can do to prevent that. My soil is decomposed granite (DG), and therefore very fast draining. Plumeria seem to tolerate a bit of cold, but cold and wet at the roots is a big problem, so the drier you can keep your plants when they have no leaves, the better.
To protect my in-ground trees, I place pipe insulation around the tips and base of each tree. If the temperatures are predicted to be in the low 30s overnight, I cover the trees with sheets or frost cloths. The cloths should not be wrapped at the base; it's better to leave them tent-like, holding them in place on the ground with bricks, etc. This way the tent can capture the earth's stored heat. Some people also string small holiday lights on their Plumeria to add a bit of warmth. You can build a mini-greenhouse around your tree by building a wood frame taller than the branches and covering the sides and top with heavy plastic. Don't let the plastic touch the branches.
Some ideas to keep the trees warm, dry, and generally safer during winter are: