Frost on Nandina

Trees and Cold Weather

Native trees tend not to be too susceptible to the cold here in central Florida, UNLESS they are native to southern Florida, and the gardener, who is terribly susceptible to the allure of nursery catalogs, has allowed them to outgrow their pots and put them into the ground.
Mea culpa!

As a consequence, I keep an eye on the weather report, watching for the dreaded, but fortunately rare Canadian freight train of arctic chill air. Once I hear the whistle blow, however, I leap into action.
My Australian tree ferns are all large enough so that their hearts are up in the air. The three lignum vitae (from seed! from the Keys!) are smaller, but none the less tender. The starfruit is going to be a real problem, since it’s now 15 feet tall, and the avocado is just a baby, so it will be very sensitive to dropping temperatures (as will all the leftover grasshoppers, I hope).

This is what I do:
Over the years, thanks to yard sales and thrift stores, I have amassed a considerable collection of used sheets and towels. All these are kept in the garden shed, and checked fairly often throughout the summer in case a rat has decided they would make good nesting material. (We have LOTS of rats in our neighborhood since we have two neighbors who routinely leave out cat food. Thanks, folks! On the other hand, there are enough rats to support a pair of nesting owls each year, so it’s not all bad.)
Anyway, I haul out the fabric, shake out lizards and insects that might be napping there, get out my collection of elderly clothespins (which I find to be generally sturdier than the cheap, imported ones), and start wrapping plants. The tree fern trunks get wrapped from ground all the way up into the fronds, and the lignum vitae turn into garden ghosts as I cover them in sheets. The avocado gets a towel around the graft zone, which is usually found close to the ground, and then a ghostly sheet overwrap, as does the starfruit. (The fabric is fastened in place with the clothespins.)
Now, let’s say that there’s fruit on one of these trees. The starfruit often fruits all winter, so that’s a possibility. In that case, I will string small, holiday lights (the kind that get warm when they’re on!) through the lower branches before draping the trees with sheets. The lights stay on as long as the temperature is low in order to create a cocoon of warm air. (It only has to be slightly above freezing to be warm enough.)

The last thing I do, while the lights are still off, is water thoroughly, so that the soil around the roots will stay above freezing and perhaps radiate a bit of heat up into the plants. Watering can take place at any time during a cold snap, so I often start this procedure the first day that I hear of oncoming cold. My garden’s water comes from underground and will be quite a bit warmer than Canadian air.

I don’t use plastic, except as an overcoat to block the wind. If the plastic touches a branch or leaf, it will transmit the cold to that spot. Fabric, on the other hand, has tiny air pockets in it, and can safely touch the leaves.
By the way, some tropical trees are more resistant to cold when they get larger. That is why one sees large jacarandas, poincianas, avocadoes, mangoes, and litchis, but rarely tiny ones. They are big enough to keep air around themselves on the rare occasions that the mercury really dips. In addition, city trees have the warmth of human dwellings to protect them. That’s why one should plant a tender tree on the south side of a home – so that the house will divert cold air in the winter. I have followed this rule carefully – all my tropicals are protected by buildings.
Just in case.

Now, normally I’d attach pictures to this blog. However, it’s been so long since a real freeze that I have no pictures to share! Yay! Here are some links to articles about protecting plants from frost:
Preparing the landscape for cold weather
Cold Protection of Landscape Plants 
Cold damage on palms 
Cold protection of ornamentals 
Fighting Florida’s Fickle Frost

Celia Beamish is a Florida Master Gardener in Polk County.

For more information, contact UF/IFAS Extension Polk County at (863) 519-1041 or visit us online at http://polk.ifas.ufl.edu.  The Plant Clinic is open Monday-Friday, 9:00 am-4:00 pm to answer your gardening and landscaping questions. Visit us in person, give us a call, or email us at polkmg@ifas.ufl.edu

The Florida Master Gardener Program is a volunteer-driven program that benefits UF/IFAS Extension and the citizens of Florida.  The program  extends the vision of the University of Florida/Institute of Food and Agricultural Sciences, all the while protecting and sustaining natural resources and environmental systems, enhancing the development of human resources, and improving the quality of human life through the development of knowledge in agricultural, human and natural resources and making that knowledge accessible.

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