Cold Temperatures and Woody Plants

Rhododendron in winter

After the cold weather of winter some plant-lovers are worrying about the health of their shrubs and trees. Plants in their native range that typically experience harsh winter conditions should be just fine if they are healthy otherwise. All plant species native to temperate regions have mechanisms for tolerating cold conditions to some degree. They have to!

Examples of amazingly cold-tolerant species

  • Sugar maple
  • River birch
  • Black willow
  • American elm
  • American basswood
  • White spruce
  • Mugo pine
  • Swiss stone
  • Lodgepole pine
  • Scots pine

How plants respond to cold

tree covered in snow
Trees have many adaptations that help them survive when cold weather hits.

Trees and shrubs have many adaptations to survive during cold weather. One way cold can injure plants is when large ice crystals form. Plants can actually prevent ice crystal formation and the related dehydration. To do this, plants accumulate solutes in their tissues, thus decreasing the freezing point of water. This process helps ensure large ice crystals can’t form and “rob” the plant of needed water.

Another way that plants tolerate extremely cold conditions is to synthesize proteins such as dehydrins that act as scaffolding for cellular membranes and heat-shock proteins that stabilize cells and tissues.

The last major response of plants to extreme cold is to alter the lipid composition of their cell membranes. Under extremely cold conditions, the cell membranes of plants typically become extremely rigid and stiff. By changing out their membrane lipids to more fluid types, their cell membranes avoid this change.

All of these tactics are usually extremely effective in protecting plants from cold temperatures.

When cold is a problem for plants

Plants require time to get acclimated and re-tool their internal machinery to deal with cold conditions. This is why most winter damage on temperate woody plants is associated with sudden, drastic changes in temperature.

How to help protect plants

The first step in protecting plants from cold conditions is to be proactive. This includes tactics as simple as choosing the right species for the region, making sure there is an insulating layer of mulch to protect the roots, and covering particularly vulnerable plants with material such as burlap.

If damage occurs, pruning to remove dead sections of the plant should be performed because that damage can attract canker pathogens or borers. However, make sure not to over-prune already stressed plants. It is not advisable to take away more live tissue than is absolutely necessary.

Once the soil has warmed, the root system can be examined. If the root system appears healthy, make sure to properly irrigate and fertilize the plant. Coming out of cold damage, the plant will be focused on dealing with recovery, but over-fertilization can fool the plant and divert resources toward growth and away from repair and recovery. With that in mind, a soil test is an important step to recovery and ensuring proper fertilization.

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