Preparing Your Florida Tropicals for a Cold Snap

Gardening in Florida is a dream -- most of the time. Anyone who has gone through a cold snap in South Florida will tell you that the dream can quickly become a nightmare. Imagine going to bed with a lush, green, blooming tropical landscape and waking to masses of dead, brown foliage. I've been there. I lost a 25-year-old, 15-foot-tall areca palm to the January freeze of 2011, and I've lost countless smaller plants to lesser freezes. Protecting your tropicals when cold weather is predicted is time consuming and can be back breaking, but unless you can afford to replace your entire landscape, it's simply practical.

What Temperatures Will Kill Tropicals?

Most tropical plants are hardy above 40 degrees Fahrenheit, but will sustain damage between 40 F and 32 F. Unprotected plants suffer severe damage below 32 F, but when the mercury dips below 25 F, you may have dead plants. The rule of thumb is to protect tropicals from freezing temperatures lasting more than 5 hours. If temperatures are dropping into the 20's, indoors is the safest place for them.

Before you do anything to protect your plants, water them well at least 8 to 12 hours beforehand. Well-watered plants withstand cold better than water-stressed plants.

Covering Your Tropical Plants

At sub-freezing temperatures, tropical plants are damaged simply from the cold. Covering them may not prevent damage, but may keep them alive. Sheets are sufficient protection between 40 F and 32 F. For lower temperatures, blankets are best.
CAUTION: Use plastic as a last resort. It's essential to remove it early before the sun starts to heat up the air underneath. I learned from experience that leaving plastic on plants during the day will fry your foliage.

Bring Your Potted Plants Indoors

Potted plants are especially susceptible to root damage and death during extreme cold weather, and are safer indoors. I had several very large terracotta containers that could not be moved, and I saved those plants from sure death by packing newspaper tightly around the base of the plant and wrapping them in several layers of blankets. I still had some damage, but the base and roots survived, so the plants grew back.

If you can't possibly bring your plants indoors, group them close together against the outside wall of a heated room, preferably on the south or west side of the house. You can also group them against the trunk of a large evergreen or live oak tree. Cover them with a couple of layers of blankets anchored well to the ground to keep cold ground-level air out.

Digging and Moving Tropicals Indoors

If you have tender tropicals that can be dug and brought under shelter, that is the best way to save them. I used to regularly dig bananas, plumerias, and brugmansias and stash them in the garage during cold snaps. Water them well beforehand, then wrap the damp roots in layers of newspaper before bringing them in from the cold. I always keep 5-gallon buckets to re-pot large plants in such emergencies. In Florida, garage is usually warm enough to keep the plants safe. Your car will survive a freezing night, but your plants may not. Bananas can also be buried in trenches to protect them. If you can't dig the plants, protect the roots by piling up mulch a foot thick around them and covering the root area and as much of the plant as you can with blankets. Cutting the plant back severely to allow covering is better than losing it. As a last resort, take cuttings to restart the plants you couldn't save.

Insulating Tropicals with Ice

Driving through northern parts of Florida, you'll see citrus groves with tall sprinklers that reach up above the trees. When cold weather threatens their crops, these sprinklers run overnight, and the ice formed around the trees and fruit insulates them. You can mimic this at your own house by leaving sprinklers running over your tropical fruit trees. A simple oscillating sprinkler can cover a large area and possibly save some precious landscaping.

This is a lot of work, but if you love your plants like I do, you'll want to protect them like they were your children. Better safe than sorry is my motto where my tender tropicals are concerned.

References:

University of Florida IFAS Extension: Cold Protection of Ornamental Plants
University of Florida: Cold Weather Protection for Vegetables and Tropicals in South Florida