Helping Your Plants Come Back After a Freeze
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Here in Jacksonville Beach we walk a tenuous line between subtropical and more temperate gardening. Its tempting to want to grow many tropical plants which will live fine for several years until we’re hit with the occasional harsh winter. The extent of damage from frost and freeze depends on the length of time in cold temperatures, the degree of cold and the type of plant. Damage can range from simple leaf tip “burn” and discoloration to tissue death all the way to the crown and roots, and it can take more than a week for it to show. Plants respond to cold by removing water from their tissues to avoid the cell rupture which occurs when ice crystals form in their cells, but this can also lead to desiccation (drying out) of the plant, especially when coupled with dry winds. Many of the plants we sell here, which are more subtropical than truly tropical, can take a light freeze if it is not too long in duration. Leaf burn, discoloration and even leaf loss are common responses, but it doesn’t necessarily mean you’ve lost your plant. Here are some tips for dealing with tender plants that may have experienced a freeze:
Herbaceous Plants: After a freeze, keep the root zone moist during the remainder of the winter and lightly fertilize toward early spring. Damaged growth on herbaceous or non-woody plants, such as cannas, elephant ears, birds-of-paradise, begonias, philodendron, pentas and gingers, may be pruned back to living tissue for aesthetic reasons but it is usually better to wait until the threat of another freeze is past. The damaged areas can help protect the rest of the plant. Also, pruning too soon may cause the plant to expend energy to leaf out with new vegetation which would be killed back again in a subsequent freeze. However, if the damaged tissue is oozy, mushy, slimy and foul smelling, it should be removed. You may remove the damaged foliage from banana trees but do not cut back the trunks (new growth will sprout from the trunks) unless you can tell for sure they have been killed. Usually this takes temperatures in the teens. A dead trunk will look brown, feel mushy, loose in the soil and will bleed a lot if punctured. With many of these herbaceous perennials it is a waiting game to see if they will emerge again after dying back. Some have fleshy below-ground parts, such as bulbs or rhizomes, which will survive and grow next year. Also, don’t expect plants which were covered with freeze cloth to look perfectly unscathed after a freeze. They can still exhibit some damage, especially if leaves were in contact with the cloth, but it is much more likely they survived.
Woody Plants: With a mild cold spell, leaves may wilt. With greater cold, woody plants usually lose their leaves. Some woodies like bougainvillea can die to the ground and resprout in spring. Make sure the plants have water the rest of the winter and in late winter apply a light fertilizer. Dead leaves can be picked off to make things look neater but delay hard pruning of woody tropical plants, such as hibiscus, tibouchina, angel trumpet, croton, ixora, schefflera, bougainvillea, copper plant and rubber tree, until new growth begins in the spring. At this time, you can lightly scratch the thin bark on a twig to see if it is green (alive) underneath. Use sanitized pruners, start at the top or tips and work your way down to live areas. Prune dead stems and canes all the way back to the base or trunk. Prune partially living branches to a juncture.
Young trees or those with thin bark can also be affected by cold temperatures. When sudden drops in night time temperatures fluctuate with day time heating from the sun, frost cracks can form on the trunks. These are not always visible until spring and unless they are ragged, will heal themselves. Ragged frost cracks can be repaired by carefully cutting away the torn or loose bark, smoothing out the edges with a knife so the tree can form a callous on its own.
Succulents and Cacti: These plants have different tissue than woody or most perennial types. Freezing can cause massive cellular damage in thick pads and stems although many of these plants are quite hardy. Don’t immediately cut off foliage or stems on damaged succulents. Instead, watch them for several weeks. Pull gently on interior leaves to see if the core is damaged on plants like aloe and agave. If interior leaves pull out easily and are mushy and black at the base, the plant has died and should be removed. If you see signs of new leaves and growth, the plant is salvageable.