LEAFLET NO: 604
Revised 9/93 -- Author Reviewed 4/96

PROTECTING PLANTS FROM COLD DAMAGE

M.A. Powell
Extension Horticultural Specialist
Department of Horticultural Science
North Carolina Cooperative Extension Service
North Carolina State University

During the winter months it is necessary to offer protection to certain North Carolina landscape plants. Winter protection does not mean to keep plants warm, as this is virtually impossible but to provide protection from damaging wind, heavy snow and ice, the alternate freezing and thawing of the soil beneath the plants and heat from the sun on very cold days.

Protection should be offered to evergreen plants by reducing water loss. Plants transpire water through their leaves. Evergreens continue to lose water during the winter, therefore moisture must be taken up by the plants' roots. Homeowners are more conscious of watering shrubs during the summer months and often this garden chore is neglected during cold weather. The roots will absorb moisture when it is available but when the ground is frozen or during a dry period the moisture is not available. The plants continue to transpire water but at this time draws moisture from living cells. If too much is given off from this source the cell dies. Consequently leaves brown out and die.

High winds and a warm sun on cold days result in a higher rate of water transpiration. Protection could be offered by planting susceptible plants in a sheltered location and providing additional water during dry periods or prior to expected hard freezes.

Foundation plantings are often injured by ice and snow falling from the roof on their frozen branches. It is sometimes necessary to construct a temporary shelter for shrubs in a precarious situation.

Wide tape or cloth can simply be wrapped around an evergreen to prevent broken branches. This is quite helpful to boxwoods and arborvitaes. If branches are bent and broken over by heavy ice or snow it is advisable to wait a few days before pruning and cleaning up. Often branches will recover to a degree of satisfaction on their own--so don't be hasty to prune drooping limbs.

An additional layer of mulch is usually recommended during winter months after the first freeze. Mulches will reduce water loss from the soil thus aiding in transpiration, and also reduce 'heaving' of the soil as the soil freezes and thaws.

To protect plants from cold damage, the following 6 steps are suggested:

  1. Plant only varieties that are hardy to your area.
  2. If you have a choice, locate less hardy plants in the highest part of the yard. Cold air settles to the lowest part of the yard.
  3. Protect plants from cold wind. A fence or tall evergreen hedge of trees or shrubs gives good protection.
  4. Shade plants from direct winter sun, especially early morning sun. Plants that freeze slowly and thaw slowly will be damaged the least. Obviously, the south side of the house with no shade is the worse place for tender plants.
  5. Stop feeding plants quickly-available nitrogen in late summer. Let them "harden off" before cold weather.
  6. A covering of plastic is excellent protection. Build a frame over the plant or plants, cover with plastic and seal plastic to the ground with soil. Shade plastic to keep temperature from building up inside. This plastic traps moisture and warm air as it radiates from the soil. It also knocks off cold wind. Be certain not to allow plastic to come in contact with plants.

Repair to Storm Damaged Plants

Knowing how and when to offer first aid to an ice, snow, or wind damaged plant will often save the plant from future decay and possible loss. Do not be in a hurry to start pruning a branch which is bent out of shape. Often in a few days following the damage the plant will straighten up on its own. Broken limbs can be pruned immediately. Make clean cuts with sharp tools. If the plant is completely misshapen after the corrective pruning - consider pruning the entire plant where the subsequent growth will be in balance.

Trees can be straightened by cabling or guying. Straighten them by attaching a cable or guy about 3/4 of the way up - pulling them back into position. Be certain to pad the tree to protect against wire damage.

Trees which are uprooted should be immediately straightened and staked. Remove any damaged roots or limbs by pruning. Keep the tree mulched and watered during stress periods.

Published by
North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.