Q: After two winters of covering and uncovering plants multiple times, and losing many in the process, I would like to replace my lost plants with those that can withstand 20 degrees as well as our hot summers. Can you provide a list of plants that can handle both? — R.K., Houston
A: There are many evergreens that will add a sense of permanency to your garden. Those that take hot or cold include azaleas, boxwood, camellias, wax myrtle, Chinese mahonia, cephalotaxus, cleyera, cryptomeria, Indian hawthorn, junipers, ligustrum, loropetalum, various viburnums, hollies (trees and shrubs), yew and roses. Some gardeners cover azaleas and camellias, especially when in bloom, during a hard freeze. The plants will survive covered or not, but frost will ruin any flowers. I never cover the other shrubs.
Perennials that tolerate temperature extremes include coneflowers, daylilies and leopard plant, which is a shade plant. Mine survived without cover. Lantana leaves burn without cover, but regrow in spring.
Root-hardy shrubs that behave as perennials may suffer damage to their tops during a hard freeze but will return from the roots in spring. These include hamelia (hummingbird bush) and duranta (golden dewdrop). Angel’s trumpet (Brugmansia) is a root-hardy large shrub small tree. I don’t bother covering these, since they become quite large during our long growing season. And since our winter is short, new growth is popping up before long.
Q: After the recent freezing rain, sheet-covered plants were encased in a shroud of ice. Will they die, or does this offer more protection? — A.B., The Woodlands
A: I found my potted cool-season bloomers beneath frozen sheets to be in good shape. The iced sheets acted like a shell that offered more protection. More tender plants may not always fair as well when covered in an extended freeze when covered.
The mistake some make is placing plastic next to the foliage. This can burn the leaves when temps drop.
Q: Is it safe to leave plants covered when another freeze is forecast within a week? — R.W., Houston
A: I leave sheets and blankets if a second freeze is forecast within a day or two. But a week with reduced or no light is a long time, so I remove covers and also check the soil to see if I need to water. It should be OK to leave row cover over plants for a few days, especially if it’s chilly. This lightweight material allows light and water to penetrate.
Q: We planted two Indian laurels last year. They shot up to 12 feet and were bright green. After the freeze, the leaves are purplish brown. What’s going on? — S.C., Bellaire
A: Cold temperatures burned the leaves. Just let them be for now. Keep the soil moist and mulch, if you’ve not already done so. More freeze damage may become obvious later. Branches and stems may be damaged, too. When the weather’s warmed in spring, you can prune back to live wood if necessary.
The tree I know by this common name is Ficus microcarpa nitida, which is cold hardy to 20-25 degrees. Newly planted trees are more prone to freeze damage.