Daniel Gill, Merrill, Thomas A. | 4/21/2005 8:11:57 PM
By Dan Gill
LSU AgCenter Horticulturist
If we Louisiana gardeners used only plants that are hardy in our area, we would never have to cover them or be worried about them when it freezes.
Gardeners trying to minimize maintenance, and those who consider covering and uncovering plants a major hassle, certainly should consider reducing or eliminating tropicals in their landscapes.
But, for the rest of us, tropical plants are worth the extra effort it takes to get them through the winter. Their ability to thrive during the intense heat and humidity of summer and the beauty of their foliage and flowers ensure that many gardeners will put up with the effort to protect them – as well as the sad, brown foliage that results from winter freezes.
Tender perennial bedding plants are another group that are severely damaged or killed by winter freezes. These include impatiens, wax begonias, pentas, blue daze, scaevola, periwinkle and coleus.
These plants can survive relatively mild winters across the state. I’ve seen wax begonias and pentas survive in Shreveport, on occasion. And in South Louisiana, it is not uncommon for these plants to survive, especially in a protected situation.
Although it’s nice when they make it through the winter and provide another year of flowers in our landscapes, we must remember these plants are not intended to be permanent.
Check for signs of life at the base of these plants after a freeze. If you still see some green, cut the plants back to the living parts, and don’t forget to mulch over or cover them should we have additional freezes. If yours have been killed by sub-freezing temperatures, remove the dead plants from the bed and mulch over the area to keep it looking neat.
You also could prepare the bed and plant hardy, cool-season bedding plants such as pansies, dianthus, alyssum, snapdragons, petunias or many others anytime from now through February for an outstanding display this spring.
I’ve been getting questions from gardeners about how to handle their plants as a result of the freezes we’ve experienced so far. Here’s some general information on what to do after a freeze is over.
–If you moved container plants into a protected location in a garage or indoors, move them back to their location outside unless you intend to keep them inside for the rest of the winter. If you will keep them inside, make sure they are close to windows and receive plenty of light.
–For plants that you covered, remove or vent clear plastic covers on plants to prevent excessive heat buildup if the next day is sunny and mild. You do not need to completely remove the cover if it will freeze again the next night. You may leave plants covered with blankets or sheets for several days without harming them, but eventually the cover will need to be removed so they can get light.
–Do not prune anything for several days after a freeze. It often takes several days for all of the damage to be evident. Damaged growth on herbaceous or non-woody plants, such as cannas, elephant ears, birds-of-paradise, begonias, impatiens, philodendron and gingers, may be pruned away until you get back to living tissue. This pruning is optional, however, and is done more to neaten things up than to benefit the plants. On the other hand, if the damaged tissue is oozy, mushy, slimy and foul smelling, then it should be removed. Make sure the base of these plants is mulched at least 6-inches to 8-inches deep to protect the crowns, rhizomes, bulbs and roots. This will help ensure their survival.
–You may remove the damaged foliage from banana trees, but do not cut back the trunk unless you can tell it has been killed. If that’s the case, it will look brown, feel mushy, be loose in the soil and will bleed a lot if punctured. The exception on not cutting back the trunk would be any banana trees that produced a bunch of bananas last year. They will not send up any more new growth from those trunks, and should be cut to the ground to make room for new shoots that will grow this coming summer.
–Dead leaves on woody tropical plants, such as hibiscus, tibouchina, angel trumpet, croton, ixora, schefflera, copper plant and rubber tree, can be picked off to make things look neater. These plants are not as common in northern Louisiana, but I have talked to gardeners growing hibiscus and angel trumpets in northwestern Louisiana about cold protection.
–If you can clearly determine what branches are dead on a woody plant, you can prune them back. Try scratching the bark with your thumbnail. If the tissue underneath is green, it’s still alive. If the tissue is tan or brown, the branch is dead. Start at the top and work your way down to see how far back the plant was killed. Generally, it’s a good idea to 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.
Finally, remember we may see additional freezes before it’s all over. Protect what you can when protection is needed. Don’t be too quick to dig up and remove tropical plants that have been severely damaged and appear to be dead. They may eventually sprout again from the base of the plant or the roots in April or May.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.