Plant survival when Mother Nature says freeze
By NEIL SPERRY, posted in the FW Star Telegram
The arctic blast that has dropped temperatures into the low teens and the wind chill to around zero degrees means gardeners need to take extraordinary precautions to protect their plants.
There is some good news. Because North Texas has had several fairly strong cold spells in the past several weeks, plants have been “hardened,” that is preconditioned to tolerate the lower than normal temperatures. Also, moisture levels of the soil before, and during, hard freezes help determine the extent of damage that may be done. Dry plants usually suffer far more damage.
The best protection for plants are covers that can range from frost cloth to burlap and old sheets and blankets. They will help hold the solar warmth in the soil and around your plants and protect against the harsh winds. Secure the frost cloth using bricks, river rock or other heavy anchors
But don’t use plastic. It traps the sun’s heat the morning after a hard freeze, and plants thaw out too rapidly. Damage below plastic covers is usually far worse than with even uncovered plants.
Here are some guidelines for protecting plants:
Winter annual color. Pansies are the most winter-hardy annual plants, usually surviving even when temperatures dip into single digits. Pinks and snapdragrons are next most durable, followed by ornamental cabbage and kale. But cover them, nonetheless.
Container plants. In general, you give up about two Hardiness Zones when you grow plants in containers. In other words, it’s like growing those same plants in an environment that is 20 degrees colder. Most landscaping shrubs become vulnerable when they’re still in pots when it turns really cold, which is why nurserymen keep them gently heated (38 degrees Fahrenheit) in greenhouses during the winter. If you have winter color container plants, or if you have shrubs and other woody plants in pots, move them into a very protected location, or wrap their soil balls with insulation.
Tender perennial species. Every part of Texas has one or more types of perennials that are marginal in their winter hardiness for that region. Mulch over their beds to improve their chances of making it through the cold. Shredded tree leaves, compost, pine straw or pine bark mulch can all work, as will frost cloth.
New ground-cover plantings. If you have just planted Asian jasmine, star jasmine, ardisia or other type of groundcover that can sustain freeze injury, improve the odds of survival with a little extra care. If they’re dry, water them ahead of the freeze. Cover them with shredded tree leaves, compost or frost cloth until the severe cold has passed. Once established, these plants may be reliable in your area, but young plants won’t have the same extensive root systems.
At-risk woody shrubs. For much of Texas, it would include oleanders, loquats, pittosporums, certain palms, waxleaf ligustrums, gardenias and fatsias. If you are able to cover these plants, you will greatly improve their odds of surviving without severe leaf burn or even total loss of the plants. Secure the cover to the ground, so that warmth from the soil can be released and trapped beneath the cloth.
Living Christmas trees. Anytime you take a plant from a 70-degree room and plunge it into subfreezing weather, you greatly increase the chance that it will freeze, even if it’s normally winter-hardy to your area. The plant is no longer hardened. If it’s already in the ground, cover it to protect it. If it’s still in a pot, set it in the garage for a day or two.
Standard plant species for your area. If you have chosen plants that are listed as hardy to your zone, or to one that is colder (smaller zone number), you should be fine. Again, water before the cold if the plants are dry.
Greenhouses. Your goal during extreme cold is just to keep things at or above 40 degrees. If you’re using electric heat, or if you have a gas heater with a blower fan, have a backup heat source in case the power goes out. If you’re moving plants into the greenhouse, remember that most tropical plants will last only 30-60 seconds in subfreezing weather before they may be lost entirely.
If you have woody plants that appear to have been damaged by the cold, don’t overreact. Sometimes, only leaf tissues are damaged, and the plants come back in the spring. When stem tissues are damaged, perhaps even to the ground, pruning may be needed, but you should wait until March to assess the magnitude of any damage. You’ll know if there is damage because stem and twig tissues will blacken, shrivel and turn brittle. In that case, trim away that winter-killed wood. Otherwise, wait until early spring to determine your next steps.
Remember to turn off your sprinkler system and disconnect all hoses from faucets. When hoses are left attached to older types of faucets during freezing weather, the water freezes within the faucets and often ruptures the pipes inside the walls of the house.
Small water features, such as ceramic pots and fountains, should be drained and dried.
For in-ground ponds without wildlife, pull the equipment, drain and store dry until warmer weather. In-ground ponds with wildlife/fish: Be sure the filter is working, and leave pond equipment running. You are relying on water movement to prevent freezing.
Swimming pools: Freeze-guard equipment should keep things running when temperatures are below freezing. If you do not have that type of protection, turn the equipment on and leave it running during the cold spell.