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Cold-weather do's and don'ts with your plants

If you prepared for the cold, dry Arctic blast last night by watering your sensitive plants and sheltering them with sheets, blankets, tarps or other coverings, you may have beat winter's frigid blast. But in areas where low temperatures dropped well below freezing for hours, the botanical carnage could appear grim. Temperatures will remain cold tonight and tomorrow with a gradual warmup for the weekend. We could see that pattern of warm to cold and back to warm into March.

What to do now

If plants are covered with frost, gently water them to melt the frost before the sun scorches tender foliage.

Keep soil moist around the plant but not soggy.

If the soil in potted plants is frozen, add water to thaw.

Cover inground plants up again when temperatures begin to drop late this afternoon. Use sheets or blankets and make sure they touch the ground to trap heat. If you use plastic, don't let it touch the plant because it's a cold conductor.

Indoor-outdoor lights, such as a strand of Christmas lights, can be placed under the covering to warm the space by about 3 degrees. Don't allow lights to touch the cover or plant which could become a fire hazard.

Turn off the automatic irrigation system so plants are not watered during another freezing night.

If you haven't already, bring potted plants inside or in your garage.

Tropical plants are at risk, new plants that aren't established in the landscape, any plant that is potted, any tender new green growth on a plant (which sprouted because you pruned in winter, which isn't a good idea).

Some of the most vulnerable plants

• Copperleaf, banana, papaya, poinsettia, hibiscus, ixora, dwarf schefflera, carissa, philodendron, croton, bougainvillea, allamanda, seagrape, bromeliads, tropical fruit trees and any other tropical or semi-tropical plant you may have planted.

• Most other fruits and vegetables, especially berries, bananas, lettuce and tomatoes.

• Most annuals, especially begonias, marigolds, and impatiens.

• Most herbs, especially those with nonwoody stems such as basil.

Additional information can be obtained by accessing the University of Florida/IFAS publication Cold Protection of Ornamental Plants on the Internet at http://edis.ifas.ufl.edu/MG025.

Here's what to do (or not) over the next few days.

Triage the plants

In the aftermath of a freeze or hard frost, your woody plants may be looking haggard and their leaves could turn brown. But don't give up just yet. Experts caution against removing or severely pruning cold-damaged plants for at least several weeks. Give them time to bounce back. Watch for new growth in the spring, then prune branches back to the green tissue.

Soft herbaceous plants are another story. If yours were blasted by the freeze, they've probably collapsed into a pile of mush, which you should remove to prevent decay-related problems. Keep the roots in the ground, though, in case new growth emerges in the spring — often the case with banana plants.

Experts say most plant tissue freezes at 28 degrees, but some plants are less cold-hardy. In the vegetable garden, vegetable plants such as squash, tomato, eggplant and snap beans freeze at 30 degrees. If your veggies are mush, you'll find plenty of new starter plants at the local garden center.

Assess the grass

Frost-covered lawns might delight kids who can slide on its icy surface and even make frost angels, but if yours is St. Augustine, it's probably not so happy. The popular turf is cold-sensitive, and may start to look wilted with a white cast that eventually turns dark brown and smells putrid. Resist the urge to water it back to health; you won't, and you'll only waste water. Come spring, you'll know whether your lawn will bounce back or require repair.

You can test your turf for cold damage now using this approach from turfgrass experts at the University of Florida: Remove several 4- to 5-inch-diameter plugs of sod from the lawn, place them in a sunny, warm location such as a windowsill and watch for new growth. If you don't see healthy-looking new growth within 30 days, your lawn has probably sustained cold damage that will require repair.

Monitor palms

Palms, especially cold-sensitive ones such as the coconut, can be damaged by freezing temperatures which destroy tissue that can't be regenerated and weaken the plant. It's like having a weakened immune system; if a palm is lackluster, it's susceptible to attack by pests and disease, which ultimately lead to its demise.

You can remove cold-damaged fronds (never green ones) now and watch for new growth from the crown in the spring or summer. If the new fronds suddenly collapse, the palm is most likely unable to conduct water through its trunk — a result of freeze damage that's lethal. Researchers at the University of Florida suggest treating cold-sensitive palms with fungicidal copper spray to prevent the pathogens that can kill after a freeze. The remedy isn't proven, but you can get details on this approach at edis.ifas.ufl.edu (search for cold-damaged palms).

Cold-weather do's and don'ts with your plants 02/05/09 [Last modified: Thursday, February 5, 2009 10:51pm]
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