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The Garden Plot for June 13, 2008
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: "Cold Temperatures in June"
The weather has been unseasonable for the first two weeks of June. That’s putting in kindly. It does not seem fair that night temperatures should be in the low 30’s. But, they have been. Just how cold can our plants take it? Plants are classified as hardy or non-hardy depending on their ability to withstand cold temperatures. Factors affecting plant hardiness include: genetics; food reserves in plant tissues; the water status of plants; and plant stress.
Gardeners can use this information to enhance plant hardiness in their gardens. Choose cultivars that are adapted to our short/cool growing season. Plant strong transplants with thick stems and well-developed root systems into healthy soil, so that plants are not left to face spring frosts without good food reserves. Keep plants threatened by cold temperatures well-watered. When it is cold, err on the side of a bit too much water, rather than not enough. Cover plants to reduce cold stress and transplant shock. Cover with breathable fabric such as remay, or with containers of water, such as Wall O’ Water. Covering plants can increase temperatures 4-6 degrees. If temperatures are at, or just below, 32 F, turn the sprinklers on and leave them on until temperatures are above 40 F. Water actually gives off heat as it freezes. Other ways to cope with cool spring temperatures include: Plastic mulches (clear polyethylene can warm soil temperatures by 15 degrees F), Raised beds, which warm soils faster, and judicious pruning to decrease shading that keeps spring soils cool.
Of course, what gardeners are asking now is: were the recent cold temperatures enough to hurt fruit and vegetable crops? Fruit crops around our area are probably fine. The following are minimal temperatures tolerated by various fruit crops at the stage during which we experienced the cold temperatures. Apples and Strawberries with small green fruit can withstand temperatures of 28˚ F. Sweet Cherry, Pear, and Plum with small green fruit can tolerate temperatures down to 30˚ F. Apricots with small green fruit should not go below tolerate 31˚ F.
Vegetable gardens are less tolerant of freezing temperatures. Cool season vegetables, such as broccoli and cabbage, can tolerate a light freeze (30oF). Warm season vegetables, such as snap bean, sweet corn, and tomato are often injured at air temperatures below 40oF and can be killed at temperatures below 32 F. The most freeze susceptible crops include: cucumber, eggplant, melon, peppers, pumpkin, squash, and basil. Signs that vegetable crops have been hurt by cold temperatures are yellow leaves and/or leaves with white, translucent spots or patches. Fruit blossoms may drop prematurely and fruit is sometimes misshapen and discolored.
After the June cold spell, the best thing gardeners can do for cold-injured, or slow-growing, garden plants is to give them a quick shot of nutrients with a liquid fertilizer root drench, such as fish fertilizer. Foliar fertilizer sprays are not as effective, especially in our low humidity climate.
For more information on plant injury due to cold temperatures, call your local county extension agent.
Helen Atthowe's new short program of gardening tips
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