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How do Drastic Changes in Temperature Affect Landscape Plants?

Written by McDonald Garden Center CEO, Eddie Anderson

Weather affects plants in many obvious ways, but also in ways we may not realize, and this winter’s fluctuating temperatures are certainly a cause for concern. Here’s an overview of the weather patterns that have occurred over the last few months and how they may affect your plants:

Prolonged Mild Fall Season Temperatures
First, a prolonged, mild, fall season did not prepare hardy plants for the winter. Plants develop their cold hardiness in stages. Each new temperature low increases the plant's ability to survive even colder temps. Maximum hardiness is usually reached in late January and early February and is best achieved by a gradual chilling. This year, the cold was delayed then hit with a vengeance. Cold temperatures can split the bark and conducting tissue of plants. The result is death of the stem beginning at the point of the split. The late warmth allowed the plant cell tissue to retain more moisture thus reducing the concentration of salts and chemicals in the cell that act as antifreeze in high concentrations. As a result, the cells freeze and burst and plant death occurs.

Drought Prior to the Cold Snap
We also experienced a period of drought prior to the cold snap. This tends to cause plants to have a more difficult time during the winter. Most likely, this has to do with root loss and limiting ability of the plant to convert sugars to starch for long-term storage in plant tissue.

Then came the snow. This is a real benefit to the plants. Snow replenishes the soil moisture and acts as a wonderful, protective blanket to help retain the warmth in the soil. What we don’t know is the depth of penetration of the cold, how deep did the frost go and what was the low temperature in the root zone. All roots die at temperatures below 15 degrees. Did the earth get cold enough to cause root damage? How much frost heave has occurred? Heaving may tear up roots and expose them to colder temperatures. Perennials and small shrubs with shallow roots are the most susceptible. As soon as the ground thaws, we recommend that you inspect plants and press them back into their original place so, the root makes good soil contact.

High Winds
During the cold, we also experienced high winds. Unless the plants were small and covered by snow, the wind pulled the moisture out of the leaf tissue. This causes severe wind burn, since the leaves are frozen and cannot replace the moisture. Next comes warm temperatures. Here is where the problems arise. The sun and warm temperatures thaw out the leaves and stems. They begin to function and have a need for water. The roots are still frozen and cannot function resulting in further dehydration. Plants that are in sunny locations are the most susceptible. Plants that are in the shade, often on the north and west side of your home, have less fluctuation of temperature.

No matter how well you plan, Mother Nature is in charge. Just be sure to stay attune to weather conditions and try to protect plants as best you can. And remember, spring is just around the corner!