02/15/2021
Hard freezes will hit New Orleans this weekend. Here's some information on protecting tender tropical plants.
WHAT TO DO BEFORE A FREEZE:
WATER
If the soil is dry, thoroughly watering landscape plants before a freeze may help them better deal with the cold. Cold weather is often accompanied by strong, dry winds. These winds may cause damage by drying plants out and watering helps to prevent this.
Wetting the foliage of plants before a freeze does not, however, provide any cold protection. Neither will a layer of ice protect plants once the water is turned off. A spray of water must continue through the entire freezing period for it to provide protection.
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. Mulches will only protect what they cover. 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 completely cover low growing plants to a depth of four inches. Leave mulch that completely covers plants in place no more than three or four days. Mulch at the base of a plant can remain in place all winter.
COVER
If they are not too large, individual plants can be protected by covering them with various sized cardboard or Styrofoam boxes.
Larger plants can be protected by covering them with fabric or plastic. Fabric coverings, such as sheets, can get wet and heavy if rains occur. Plastic would be better in rainy weather. However, wherever a leaf touches a plastic cover it will freeze. Both of these issues can be resolved by providing simple supports under the cover to support wet fabric or keep a plastic cover from contacting the foliage. 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. Clear 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. A safe, easy way to do this is to generously wrap or drape the plant with small incandescent outdoor Christmas lights (not LED lights). The lights provide heat but do not get hot enough to burn the plant or cover. Please be careful and use only outdoor extension cords and sockets.
If necessary, you may prune back a large plant, like a hibiscus, to make its size more practical to cover. For trees, such as palms and 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. For palms, the trunk must be wrapped from ground level to the base of the leaves to protect the trunk and crown.
