SAN ANGELO Ice and cold have gripped much of the state for several days, leaving many Texans to wonder about what’s to become of their frozen landscapes.
John Begnaud, Texas Cooperative Extension horticulturist in San Angelo, said in addition to low temperatures, the duration of the cold also is a significant plant-damaging factor.
“We’re in USDA (U.S. Department of Agriculture) plant hardiness Zone 7B, so we can historically expect an average annual minimum temperature of between five and 10 degrees Fahrenheit,” Begnaud said. “Duration of cold, especially temperatures below freezing, can allow plant tissues to be more deeply penetrated by low temperatures. This can harm marginal plants to our area such as oleander, some palms and even perennials such as lantana and plumbago.”
The extent of the damage may not become apparent until bud-break in March or early April, he said. Some injury may not appear until the plants are stressed by summer’s heat and dry weather.
Oaks, pecans, nandina, hollies and others will show no damage because they are well suited to the extremes of Zone 7B, Begnaud said.
“Deciduous trees and shrubs are likely to see little or no damage from ice,” he said. “Evergreen plants such as ligustrum, boxwood, Indian hawthorn and especially pittosporum may show browning of leaves with irregular discolored patches. Some evergreens respond with tarnished or bronzed foliage. This will be particularly noticeable on the youngest or newest leaves. This damage may remain on the plant throughout 2007 unless removed by pruning after new spring growth appears.”
Begnaud recommends removing ice from plants only when it may cause limb breakage. Thumping or bumping is the method he recommends. He said a rapid thaw, such as that caused by pouring hot water over a plant, may cause ice crystals to pierce plant tissue and actually increase the damage.
Current conditions demonstrate the need for proper planting of evergreens, Begnaud said.
“Shadows cast by evergreens such as live oak trees slow the thawing process during cold spells,” he said. “Trees that shadow streets and homes don’t allow the sun to warm and melt accumulated ice for another day or two, thus promoting the chance of damage from a prolonged cold snap. That’s why we always recommend planting evergreen trees on the north or east side of a home and deciduous trees on the south and west sides. This has a definite affect of allowing the sun to warm your home in winter, which not only will help your plants, but your heating bill as well.”