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Thursday - December 10, 2009

From: Leander, TX
Region: Southwest
Topic: Pruning, Seasonal Tasks
Title: Cutting back woody plants after freeze in Leander TX
Answered by: Barbara Medford


I have several woody shrubs in a prominent location. Now that the leaves have frozen, how far back should I cut them? These are Flame Acanthus, Salvia ballotiflora, and Aloysia macrostachya, but I wonder about winter pruning of all woody perennials and shrubs.


We have three questions on the docket regarding what to do after the sudden hard freeze that occurred recently in Central Texas; in fact, we are still dipping below freezing at night frequently.With your permission, we will address all three first as a group, and then, for each question, the individual plants involved. One thing that applies in every case is, don't fertilize. Plants should be fertilized in the Spring, when you want to encourage new shoots to appear. The last thing you want to do is encourage new shoots now that will put more stress on already-stressed roots and probably just get frozen back again.

You may already know what happened; actively growing plants still have water in their upper structure, particularly the leaves. A sudden hard freeze causes that water to expand, bursting cell walls in the leaves, and they quickly turn dark and look pathetic. What made this freeze worse was that it was earlier than we ordinarily expect these conditions in this part of Texas, very sudden, temperatures went down very far, and remained below freezing for several hours. A gradual decrease in temperature over a period of time increases the ability of plants or plant parts to withstand cold temperatures. A sudden decrease in temperature in late fall or early winter usually results in more damage than the same low temperature in January of February.

In your case, you are asking about woody perennials that are deciduous anyway, and will profit from being pruned back. From Texas A&M AgriLIFE Extension this article Follow Proper Pruning Techniques will give you some good information on what and when to prune. If you elect to prune now, in the interest of appearance, wait a few days first, as more damage may become evident as time passes. As far as the specific plants you asked about, here is the information we could find on what kind of winter care they need. By the way, thanks for giving us the specific names of each plant, and for having all Texas natives. Our kind of gardener. 

Anisacanthus quadrifidus var. wrightii (Wright's desert honeysuckle) - In the United States, this plant is considered endemic to Texas, and appears as a native mostly farther west and south than the Central Texas area. However, according to our Native Plant Database, "This plant is drought tolerant and cold-hardy. Cutting it back severely in the winter will provide more blooms and encourage a bushier form." It is considered hardy from Zones 7b  to 11 and hardy to 5 deg. F. The Leander area is generally considered to be Zone 8a, so we think your flame acanthus is safe.

Salvia ballotiflora (shrubby blue sage) -Apparently, this plant is also endemic to Texas, but is found growing as a native in Central Texas. We learned that it has a high tolerance for heat, but no specific mention of its tolerance for frost; it is root hardy to Zone 8, so give it a good prune and it will rise again.

Aloysia macrostachya (Rio Grande beebrush) - Again, from our Native Plant Database: "This plant may freeze down to ground 1 in 5 winters, but will re-sprout again the next spring." It is found growing naturally in far south Texas and into Mexico, and is hardy to Zone 8. It is considered root hardy as far north as Austin.

From our Native Plant Database:

Anisacanthus quadrifidus var. wrightii

Salvia ballotiflora

Aloysia macrostachya





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