News Release Distributed 12/28/12

By Allen Owings
LSU AgCenter horticulturist

HAMMOND, La. – Winter is here, and this leads to many questions about protecting landscape plants during the cold months of December, January and February.

It is important to pay attention to the weather forecasts this time of year and try to know a couple days ahead of time when a freeze may be approaching. Keep in mind frosts and freezes are different. The weather conditions prior to a freeze or frost also play a role in how these temperatures affect plants.

You can do several things to help your plants survive low temperatures.

Thoroughly water landscape plants before a freeze if the soil is dry. This is especially important for container-grown plants. Shrubs in landscape beds can also be helped with irrigation prior to freezes. It would be best, however, to make sure your shrubs received adequate irrigation or rainfall during fall. Strong, dry winds that frequently accompany cold fronts 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.

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. Keep in mind that your cool-season bedding plants are adapted to the cold temperatures that are normal in Louisiana during winter, so cold protection typically is not needed.

For plants growing in the ground, mulch with a loose, dry material such as pine straw or leaves. Mulches will only protect what they cover and are best used to protect below-ground parts and crowns. Or they may be used to completely cover low-growing plants to a depth of 4 to 6 inches.

But don’t leave a complete cover of mulch on for more than three or four days. Many folks heavily mulch their tropical hibiscus in landscape beds using this method. Smaller, individual plants can be protected by covering them with various sizes of cardboard or plastic foam 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. You need 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.

For severe freezes, when temperatures dip into the teens, providing a heat source under the covering helps. A safe, easy way to do this is to generously wrap or drape the plant with small outdoor Christmas 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 a large plant to make its size more practical to cover.

You can see more about work being done in landscape horticulture by viewing the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals.

Rick Bogren