The big picture prediction for the remainder of this winter is that it will be warmer than usual and dry. However, we could still have a freeze, so read on to find out what to do for your plants before and after a freeze.
When very cold weather is forecast, the first thing to do is to thoroughly water all your plants. The reason being that moist soil will hold more heat than dry soil, which has more air spaces. If you don’t have time to do anything else such as cover or move plants, be sure to do this one thing. If you can’t water a couple days in advance, water whenever you can, even up to the night that the frigid weather is expected; it can still help!
Whenever you water, do so deeply and infrequently to encourage a large, deep, and healthy root system, which can help get a plant through some unusually cold weather. Established plants do not need to be watered more than once a week, and even less frequently during the winter months. If they don’t have leaves right now, plants cannot use much water because they are not transpiring water from their leaves. A thorough soaking every month if we haven’t gotten an inch of rain, is great at this time of year. For trees, thorough means 10 gallons of water per inch of tree diameter.
Leave the leaves and other dry plant material on the ground, they will help to insulate the soil to hold in heat and moisture. They also add nutrients and organic matter as they break down, feeding and improving the soil micro-organisms, and feeding the plants as well. Apply a two-to-three-inch layer of mulch if you don’t have enough leaf litter. Do not let the mulch touch the trunk or stem – keep it at least four inches away. Be sure to water very thoroughly if you have mulch since it will absorb some of the water.
If a freeze, or near freeze, is predicted, move potted tropical and other “tender” plants into the house or the garage, onto the porch, or at least under the eaves on the south or west side of a building. Cover them if possible.
Cover plants growing in the ground or in large pots with large cardboard boxes, bed sheets, blankets, plastic sheeting, or anything similar, or a combination of materials. The essential thing is to trap heat from the ground under the covering by making sure it goes all the way to the ground; anchor it with bricks, rocks, or other heavy things. The more ground that is included under the cover, the better chance the plant has. The thicker the covering material is, the better it will hold in the heat. And if the soil is moist, you already know it will hold more heat.
Don’t be too concerned about the cover touching the plant; although a few leaves that are touching it may be damaged, most of the plant will not be. Push a tomato cage into the ground over your more fragile plants (if they are small enough) to hold the covering material off them. Be sure to take the covering off during the day if temperatures are above 32 degrees, and as soon as the danger of frost has passed.
Wrapping a plant doesn’t protect it, except from drying winds, since the plant is not producing heat. Some people put outdoor Christmas lights, or jugs filled with water under the cover for an additional source of heat. Be sure the cover is not in contact with any lights.
Some plants will be damaged by the cold weather, some will die back to the ground but their roots will survive and then regrow next spring (these plants are “root hardy”); others will be lost to a hard freeze.
After a freeze do not be in a hurry to trim your plants except for ones that have turned to mush. Plant tissue that is mushy provides an opening for pathogens to enter, so remove mushy plants or plant parts. Cut back to where the stem is firm. Be sure to dip your pruners in rubbing alcohol for 30 seconds between cuts to keep from spreading potential pathogens to other plants or plant parts.
Wait to prune woody plants until the buds come out, when it will be obvious where to make cuts. It won’t hurt the plant to cut it earlier, but you might cut back branches that are still alive, or you might not cut enough, and will need to prune again in a few weeks. It does not help the plant to cut it early.
If you had already planned to prune shrubs and trees to control their size, or to shape them, there is no need to wait. Turk’s cap, cenizo, esperanza, beautyberry, ornamental grasses, and many other plants can be pruned lightly or heavily. However, do not prune redbud, azalea, or any other early spring-bloomers, or you will remove the potential flower buds. Oak trees can be pruned now, do not prune oaks between Feb 1 and July 1 (due to the threat of oak wilt).
For palms, never prune any fronds that are even partially green (because they can photosynthesize, and palms need all the photosynthetic capacity they can get), or fronds that are “standing up” (since they can protect the crown from strong winds).
Look around and see what plants are still looking good after cold weather – most of them will be natives. Keep them in mind when purchasing new plants for your yard. Native plants require less care-whether it is hot or cold-and provide many other benefits to the habitat.