Protecting your plants in cold weather

Protecting your plants in cold weather
MGN
Weather Talk

POSTED: Tuesday, November 12, 2013 - 1:14pm

UPDATED: Tuesday, November 12, 2013 - 1:16pm

Cold weather can harm your temperature-sensative plants. Here are a few tips from the LSU Ag Center to follow before a freeze occurs in south Louisiana.

What to do before a freeze:

  • WATER. Thoroughly watering landscape plants before a freeze may reduce the chance of freeze damage. Many times cold weather is accompanied by strong, dry winds that may cause damage by drying plants out. Watering helps to prevent this. Wetting the foliage of plants before a freeze does not, however, provide any cold protection. A well-watered soil will also absorb more solar radiation than dry soil and will re-radiate the heat during the night.
  • MOVE INSIDE. Move all tender plants in containers and hanging baskets into buildings where the temperature will stay above freezing. If this is not possible, group all container plants in a protected area (like the inside corner of a covered patio) and cover them with plastic. If plants are kept inside for extended periods, make sure they receive as much light as possible.
  • MULCH. For plants growing in the ground, mulches can help protect them. Use a loose, dry material such as pine straw or leaves. You should be aware that mulches will protect only what they cover. A mulch at the base of a bird-of-paradise will help the roots, but will provide no added protection to the leaves. Mulches, then, are best used to protect below-ground parts, crowns or may be used to cover low-growing plants to a depth of 4 inches. Leave complete cover on no more than three or four days.
  • COVER. If they are not too large, individual plants can be protected by covering them with various sizes of cardboard or Styrofoam boxes.

Larger plants can be protected by creating a simple structure and covering it with sheets, quilts or plastic. The structure holds the covering off the foliage, preventing branch breakage and improving cold protection. It need be nothing more elaborate than three stakes slightly taller than the plant driven into the ground. The cover should extend to the ground and be sealed with soil, stones or bricks. Plastic covers should be vented or removed on sunny, warm days.

The covers will work best for radiational freezes by preventing or blocking heat loss. The extreme, prolonged cold that occurs during advective freezes is not so easily dealt with. Many plants will still die, even with protection. This can be helped by providing a heat source under the covering. An excellent technique is to wrap the plant with small, outdoor Christmas lights. The lights provide gentle heat throughout the plant area but do not get hot enough to burn the plant or cover. Be sure to use outdoor extension cords.

If necessary, you may prune back a large plant, like a hibiscus, to make its size more practical to cover. For trees, such as citrus, that are too large to cover, you may at least want to wrap the trunk with an insulating material such as foam rubber or blankets. Even if the top dies, you may be able to regrow the tree from the surviving trunk.

If you are growing vegetables, harvest any broccoli, cauliflower, fava beans or peas that are ready. Freezing temperatures will not hurt the plants, but can damage the heads, pods and flowers. Also, any citrus fruit should be harvested from the tree before a hard freeze.

What to do AFTER a freeze:

After a freeze is over, check the water needs of plants in containers and in the ground. Unless you are keeping them inside for the rest of the winter, move container plants back to their spots outside.

Remove or vent plastic covers to prevent excessive heat buildup if the day is sunny. Pull back mulch that completely covered low plants.

Damaged growth on non-woody plants should be pruned away, and dead leaves on all plants can be picked off. Delay hard pruning of woody plants until new growth begins in the spring, and you can more accurately determine which parts are alive and what is dead. Don’t be too quick to dig up and remove plants that appear to be dead. On occasion, they may eventually resprout from the roots in April or May.

Tropical and sub-tropical plants can be used effectively in the landscape, but they must be protected or replaced when necessary. The best idea is to plant a good combination of tender and hardy plants. 

Click here to download the LSU Ag Center's "Commonly Grown Plants and Their Cold-Tolerance Temps." 

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