Winter is here, and it’s time to be prepared to protect landscape plants during cold snaps. The best approach is to pay attention to the weather forecasts and have a plan ahead of time when a freeze is approaching.
To prepare plants for a freeze, thoroughly water them if the soil is dry. This is especially important for container-grown plants, although shrubs in landscape beds also can be helped with irrigation prior to a freeze.
“Adequately hydrate plants gradually during the fall and then three to five days before a major cold event,” says LSU AgCenter horticulturist Allen Owings. “Wetting plant leaves 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 that’s not possible, group them in a protected area, such as an inside corner of a covered patio, and cover them with fabric or plastic sheeting.
For plants in the ground, mulch them 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.
“You also can use mulch to completely cover low-growing plants to a depth of 4- to 6-inches, but don’t leave them covered for more than three or four days,” Owings says.
Smaller individual plants can be protected by covering them with various sizes of cardboard or plastic foam boxes.
For larger plants, create a simple structure and cover it with fabric or plastic, being sure to keep the covering from touching the foliage. For example, you can use several stakes slightly taller than the plant or last season’s tomato cages. The cover should extend to the ground and be sealed with soil, stones or bricks to keep out the cold. Plastic covers should be vented or removed on sunny, warm days.
When temperatures dip into the teens, 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 that will provide heat but won’t get hot enough to burn the plant or the cover. But be careful and use only outdoor extension cords and sockets.
Keep in mind that your cool-season bedding plants and the vast majority of trees and shrubs are adapted to normal winter temperatures, so cold protection typically is not needed.
Got a gardening question? Write to GardenNews@agcenter.lsu.edu.