In winter, dry conditions can actually be more damaging than the cold itself. Cold winter air is usually quite dry, and winter winds can remove water from plants faster than the roots can absorb it. This is especially true for evergreens, as water evaporates quickly from their foliage.
In addition, if the ground freezes, the underground water turns to ice crystals which cannot be absorbed by plant roots. Even dormant plants need and absorb water year-round.
Water acts as an insulator. Plant cells that are plump with water will be stronger against cold damage. Likewise, moist soil will tend to stay warmer than dry soil, so a regular watering schedule in dry, cold weather can help protect plants from freezing temperatures.
Follow these guidelines when watering plants in freezing weather:
- If your soil stays frozen all winter, then fall is your prime time – make sure everything is well watered before the ground freezes.
- If you experience freezing weather only occasionally, and you have had insufficient rain or snowfall, water deeply a day or so before a freeze is forecast. Be sure to water the entire root system – a good rule of thumb is to water an area the size of the plant’s drip line.
- Be extra attentive to newly planted trees and shrubs. Not only are their roots less established, but the churned-up soil can allow cold air to penetrate deeper to the roots.
- Water when the air temperature is above 40° F, and don’t water if there’s snow or ice on the ground.
- Water early in the day, so the plants have time to absorb it before the temperature drops at night.
- Don’t wet the foliage. Commercial growers sometimes use sprinkler irrigation to protect plants from frost, but it requires constant sprinkling and should only be done under specific conditions.
- Be careful not to over water. Once or twice per month should be sufficient – the plants will not be absorbing water as fast as they do during the growing season, and the cool soil can easily become soggy.
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