Freezing Temperatures Could Kill Sensitive Vegetation

By San Tan Times Staff, with content originally published by Lucy Bradley, Agent Urban Horticulture

A freeze warning means sub-freezing temperatures are imminent or highly likely. These conditions could destroy or damage crops and other sensitive vegetation.

How To Protect Vegetation:

Keep plants well watered. Frost injury occurs when ice crystals form on the leaf surface drawing moisture from the leaf tissue. The damage from this dehydration will be less severe if the plant is not already drought-stressed.

Firm, bare, moist soil absorbs more heat and loses it more rapidly than soil that is loose, dry, or covered with mulch or vegetation.

Manage your irrigation carefully, keeping the moisture level as even as possible.

There are other products marketed to protect plants from frost damage. Read the label carefully.

Don’t overprotect! Plants are more frost resistant if kept hardened to cold weather.

Cover plants with cloth or paper (not plastic) to insulate. You can use sheets or blankets for minimal protection or use a frost cloth. A properly applied frost cloth can protect plants at temperatures down to 30E F, some down as low as 20E F depending on the fabric and the weave. Completely drape the plant from the top all the way to the ground. Do not allow any openings for warmth to escape. This procedure will trap the heat radiating from the soil and maintain a more humid atmosphere around the plant foliage. Optimally, the drape will be supported by a frame which does not allow it to touch the foliage. DO NOT gather the drape around the trunk of the tree. The goal is to trap heat being radiated from the ground, so ensure that the drape touches the ground at least as far out as the drip line.

If you use sheets or blankets, remove the coverings every morning when the temperature under the covering warms to 50E F. Permanently covering plants with sheets or blankets for the duration of the winter can be harmful and is not recommended in southern Arizona. Even if the temperature under the drape does not warm up enough to “cook” the plant, it is likely to warm up enough to cause the plant to break dormancy, begin actively growing, and thus become more susceptible to frost damage. Many of the frost cloths available may be left on for extended periods without risk of harming the plant.

The above information was provided by Lucy Bradley, Agent Urban Horticulture and her 1998 Frost Protection Publication. To read the entire publication on frost protection, go online: