Plant Answers

Express News Weekly Article
Saturday, December 18, 2004
By Calvin Finch, Conservation Director, SAWS, and Horticulturist

To Cut or Not to Cut

My radio colleague Jerry Parsons and I have a debate every year after the first freeze. The issue is when to cut back freeze damaged foliage. We both agree that many root hardy perennials are more attractive if they produce new stems and foliage every spring. The question was not whether to cut back the material; our debate was when is the best time to cut back the dead foliage. There are arguments supporting both the “wait to prune” and the “cut it now” tactics. You consider them and then decide what is best for each of your beds. The plants that are usually in consideration for pruning back are the root hardy perennials such as lantanas, plumbago, esperanza, firebush, poinciana and verbena. Warm weather vegetables and annual flowers can also be considered. My side of the debate is that it does not make sense in many situations to cut back freeze damaged stems and foliage immediately after the damage occurs. Here are several reasons you may want to wait to cut back the browned foliage:

The browned foliage and stems provide protection for lower unfrozen stems in the interior of the plant. If you cut the frozen upper foliage immediately, the unprotected and as yet unfrozen stems in the interior of the plant are more likely to be frozen by the next freeze. This is an important consideration if you feel it is desirable to preserve as much wood as possible so you have a larger summer esperanza or firebush. In a mild winter, peńtas may not be completely killed if the lower stems are protected by the upper foliage.

If one of your desires for your landscape is to attract wildlife, the frozen foliage and stems are infinitely more attractive and useful to songbirds, insects and other wildlife than a bed trimmed to the ground. The birds seek out insects and seeds in the winter landscape and the standing stems provide some shelter. Annual flowers such as zinnias and sunflowers are especially useful to birds if the killed flowers are left.

Our winter weather is erratic. A sunny warm spell will often stimulate new growth from plants that then become very susceptible to more severe freeze damage as the winter progresses. This is especially true of plants that did not harden off before the first freeze and are in a growth mode. Plants pruned back to green wood are more likely to initiate new growth.

Jerry is more inclined to quickly cut back the killed stems. Some arguments for a quick trimming of the killed stems and foliage are as follows:

It is neater. If you are into manicured rather than natural, the removal of browned plant material is important to you.

If you are going to replant the beds for the winter with cool weather flowers such as pansies, the frost killed stems get in the way and reduce light available for the new plants. Many gardeners also have cold weather perennials such as paperwhites and columbines or reseeding annuals such as larkspur that need the space and light. A spreading lantana or verbena may have grown over the larkspur planting. Pruning out the freeze killed stems will result in faster, better development by the larkspurs.

We often have more time in the winter to do maintenance tasks in the garden. To some gardeners it is desirable to complete as many tasks as possible now and save the time we have in the spring for planting and other tasks.

We may not agree on when to trim back freeze killed stems and foliage but Jerry and I do agree that the lawn mower should not be entirely retired for the winter. Use the mower to mow leaves that accumulate on your lawn and to keep winter weeds in control.

It is good exercise to rake leaves but it does not make any sense to dispose of them in the landfill. Burn your calories by running the lawn mower over the fallen leaves on the lawn. Chopped up by the mower, they will decompose quickly to add valuable nutrients and organic material back to the lawn. It is the environmentally responsible way to deal with leaves.

If you are blessed with large trees, the shade provided is wonderful but it means your lawn is probably not thick enough to keep out the winter weeds such as rescue grass, annual blue grass or rye grass. If you mow those winter weeds they are very attractive. Mowing frequently enough to prevent the weeds from producing seed also means that they weed pressure may be less next year.