Here we go again, having to deal with another round of devastating freeze damage. Severe cold can cause all types of problems for susceptible plants not prepared for it, especially tropicals and zone 8 evergreens from Asia. Freezing temperatures can damage tender plants by rupturing plant cells as ice crystals form and rapid changes in temperatures occur. Unfortunately, this time an insulating blanket of snow wasn’t in the cards.
The signs of cold damage can be confusing, since some damage may not be evident until months later. Leaves and tender shoots subjected to freezing temperatures appear water-soaked and wilted. These tissues will usually turn black or brown within a few days. Evergreens, such as azaleas, camellias, gardenias, and roses may have dead foliage and damaged stems. I hate to say it, but we might have lost blooms on many azaleas and most camellias as they bloom on the previous year’s growth. There could also be stem damage like bark splitting as well.
This type of damage occurs as a splitting of the stem or bark, typically near the base of the plant, due to sudden changes in temperature. Once they become obvious, split stems and branches should be pruned to unaffected growth. Hopefully, most of our damaged shrubs will at least re-sprout from the lower stems and the ground once warm weather is here. Sometimes cold injury is not readily apparent until the plant starts to actively grow again. At this point, cut out the dead and leave the living.
After a freeze or frost, the leaves of damaged herbaceous plants may immediately appear wilted and water soaked. However, the freeze injury to the twigs, branches, or trunks often doesn’t appear on shrubs and trees right away. Wait at least a month then use a knife or thumbnail to scrape the outer bark on young branches. Freeze-damaged areas will be brown beneath the bark; healthy tissues will be green or white.
Delay pruning until time reveals the areas that are living and dead and until the threat of additional frosts or freezes has passed. Leaving dead limbs and foliage at the tops of plants will help protect the lower leaves and branches from nighttime radiation loss. Pruning immediately after a freeze does not improve the outcome. Also, plants that are pruned tend to be invigorated more quickly, which may set them up for further damage in our unpredictable cycling of warm and cold temperatures.
So, do not be in a hurry to prune or remove your damaged plants. Some plants may appear dead but may not be. Corrective pruning should not be started until the full extent of the damage can be determined. Visit our Tyler Botanical Garden (in the Tyler Rose Garden) to see how the Smith County Master Gardeners are dealing with the damage.
Greg Grant is the Smith County horticulturist for the Texas A&M AgriLife Extension Service. He is the author of Texas Fruit and Vegetable Gardening, Heirloom Gardening in the South, and The Rose Rustlers. You can read his “Greg’s Ramblings” blog at arborgate.com, read his “In Greg’s Garden” in each issue of Texas Gardener magazine (texasgardener.com), and follow him on Facebook at “Greg Grant Gardens.” More science-based lawn and gardening information from the Texas A&M AgriLife Extension Service can be found at aggieturf.tamu.edu and aggie-horticulture.tamu.edu.