Are early freezes more damaging?
With the extremely early arrival of our first hard freeze in November 2018, we received lots of questions about freeze damage. Unusually early freezing weather can be particularly damaging to plants.
During our normally hot and dry summers, plants don’t grow much, so the arrival of cooler temperatures and rainfall lead to autumn growth spurts in the garden. This new growth is quite tender, with no waxy cuticle to protect the young leaves. And with no protection, these leaves are much more vulnerable to a killing frost.
In many plants, these damaged tissues may simply appear to have a slight purple tinge, because of the destruction of chlorophyll. But after a few days, the purple will turn to brown, as the dead tissues desiccate.
If possible, ignore the damage after these early frost events, as pruning may encourage new growth, and we really just want our plants to settle in and stop growing for the winter.
We often use the word “hardy” when referring to plants, and this term describes a plant’s ability to survive cold weather. You might also hear the term “root hardy” for plants that die completely to the ground each winter, then start over in spring by resprouting from the roots.
One term that was really odd to me that I heard used a lot when I moved back to Central Texas was “shrubby perennial.” “Perennial” can be used to either mean a long-lived plant, such as a tree, that lives perennially, or a small herbaceous plant that dies to the ground each year and re-emerges in spring. I came to learn that people around here often refer to shrubby plants like lantana, esperanza, and Pride of Barbados, that get very large and woody prior to dying to the ground each year, as “shrubby perennials.”
Some plants don’t desiccate and turn brown when hit with cold temperatures, they simply turn to mush. Summer annuals and herbs like basil are not hardy, so the roots die in cold temps, leaving nothing from which the plant can resprout. But other plants like purple heart and crinum, which also turn to mush, do return in spring. Herbaceous native perennials like coneflower and Salvias are hardy here in the south, and will brown on top. Cut them to the base in late winter for next year’s new rosette to form.
There are also “tender” and tropical plants like citrus and hibiscus which may be killed by freezing weather. Microclimates do make a difference, and when in doubt about a plant’s sensitivity to cold, be sure to mulch heavily and be prepared to protect during any extreme cold spells.