Frost and your Plants

What happens to your plants when there is a frost? When the temps hit around 32 degrees, water vapor freezes on the surface of plants which creates that frosted appearance. If the temperature dips below 32 degrees, water inside and outside plant cells freeze. The ice within the plant punctures the plant’s cells and will cause that part of the plant to die. A sure sign of frost damage is wilting of the outer leaves. That wilted growth will turn brown and crispy, indicating that part of the plant has died. The idea here is to keep calm and carry on. Though you may be tempted to try anything to get your plants healthy and green again, less is more.

As hard as it is to do, the best plan of action is to wait and see. Once the threat of frost is truly over, and new growth or buds start to appear, it’s time to prune. Take note that a branch may have dead leaves due to frost damage, but the branch itself may not be dead. Damage from freezing affects the leaves first, followed by the stems, branches, and roots. Live stems and branches will produce new growth, while those killed by frost damage will not. You may think that your entire plant died only to discover new growth occurring toward the base a couple of months after the last frost. It pays to wait it out. As previously mentioned, your first thought may be to get in there and cut out all that brown, crispy foliage. Don’t do it. You risk doing more damage if you remove it too soon. All that ugliness can help protect the interior of the plant from future frost. Resist heavy pruning until the plant returns to its normal growth pattern. Most plants will begin to show new growth in as little as two-to-four weeks after frost damage. Intensive pruning too soon will stress the plant further.

Watering is recommended, as it helps plants overcome shock and provides nourishment for healing and promotes new growth. However, overwatering also can be a serious issue, so be careful. Stay away from fertilizer until you start to see new growth. Nitrogen in fertilizer can make your plants leaf out too quickly, causing more stress, and the possibility of promoting fungus growth.

How to prune? The methods are different based on the extent of damage to the plant and verity of the plant. If only the outer growth has been affected, and the growth underneath has not suffered, lightly prune the damaged stems or branches using hand pruners or loppers stopping at the closest new node. If the majority of the upper growth of a plant was killed by the cold, then renewal pruning is the best way to prune. This involves severely pruning back the affected areas, often to within a few inches of the ground. Loppers and sometimes a pruning saw will be needed. Because the base of a plant and its roots are the least susceptible to injury from freezing temperatures, severely pruned plants will often grow right back.

As bad as it may seem right now your brown plants may not be finished just yet. Some patience, consistent warmer weather, and some correct pruning when the time is right just may have your landscape looking good again this spring.