Freeze Damage Prevention
1. Give your plants a “blanket” of mulch. Together with moist soil, this helps protect their roots. This is generally enough protection for woody perennials that can withstand freezing temperatures, this includes plant like yaupons, loropetalum, abelia, azalea, boxwood, Indian hawthorn, nandina, roses, wax myrtle. If it has bark it is most likely a woody perennial. Perennials like Duranta, Aucuba, hamelia, angel’s trumpet and root-hardy hibiscus may lose all or some of their tops in a hard freeze. But water and mulch, and they will likely return from their roots in spring. Tender Perennials like Fire spike, ferns, lilies, colocasia, and tropicals will die back to the ground, covering them is optional.
2. During winter months with early morning temperatures below 38°F, the freeze/rain sensor will prevent sprinklers from coming on. So you should change your start time to in the morning.
3. It is important to water your plants thoroughly before a freeze. You need to be sure the roots are wet, and preferably not the leaves. A lot of freeze damage is from dehydration. Watering before a freeze could make a big difference especially with tropicals and tender perennials.
4. Tropicals and tender perennials will fare better if they are covered. If they are not covered they may die back to the ground. They should return fresh in the spring. If you cover them remember, to be sure the roots are protected, covered, or mulched.
5. Once we hit autumn it is best to stop fertilizing tender perennials and tropicals that will remain outside during the winter. Fertilizing encourages new growth which is more vulnerable to freezing.
6. One trick for protecting new transplants in danger of being hurt by frost is to apply a foliar spray of diluted seaweed extract (one teaspoon to the gallon of water) just before nightfall when frost is expected. Seaweed administered just before frost helps stop cold damage by increasing the sugar content in plant cells, thereby lowering the freezing point of the sap.
7. Please don’t cover your plants with plastic touching the leaves. It is best to use woven frost protection sheets or sheets and blankets. In a mild freeze, one blanket or sheet will probably do for most plants. If it’s a hard freeze (below 30 degrees for any period of time) use a heavy blanket or several layers of sheets. You can even use plastic over that if you want because it won’t be touching the foliage. And remember to anchor them with rocks or something heavy on the edges of your N-Sulate or blanket so they don’t blow off in the wind exposing roots and plants.
8. It is best not to do any heavy pruning on freeze-damaged plants until late winter when you think all chance of frost is over. We wait till spring just to be sure.
9. It is important to remove all of your protective covering if the sun comes out and the temperature goes up, because it can be 32 degrees in the morning and heat up to 75 degrees and cook your plants.
After the Freeze
• Do not wash frost/ice off plants the morning after a freeze. This raises the temperature too quickly and usually damages the plant’s cell tissues. Wait until the ice thaws, then assess plant damage.
• If you have damage to your trees it is a good idea to hire a certified arborist to remove large or heavy broken branches from trees. If one-third or half of the major limbs are broken, or the trunk is split, they can advise you if it is possible to save the tree.
• Provide support for young trees bent with the weight of ice. Ice is not something we have generally have to deal with in Houston.
• After a freeze, remove limp and damaged parts on annuals and tender perennials like impatiens and crinums. Do not prune woody plants such as Durantas and hamelias. Leaving the damaged wood and leaves helps protect living part of the plant or shrub. Wait till spring to prune back to live green wood or stems.
• Once spring has arrived you can begin fertilizing to encourage new growth on damaged plants.
• Remember most plants like even moisture. It is important to water during dry periods weather it is summer or winter and refresh your mulch layer before summer and before winter to insure that the roots of your plants are protected from extreme heat and cold.