Released August 25, 2009
LINCOLN, Neb. -- Gardens can be productive well into the fall when given proper care through the growing season. With the advent of cooler temperatures, vegetable color, flavor and sweetness improve and a second crop of broccoli, lettuces, radishes, beets and mustard greens can be enjoyed. However, the highly variable temperatures in Nebraska that characterize the changing seasons can make gardeners wonder how to protect the garden from a sudden drop in temperature.
Gardeners should look at what is in the garden and identify the crops that are sensitive to frost or are "frost tender." These are often crops that originated in tropical or sub-tropical places such as the solanaceous vegetables, which include tomatoes, peppers and eggplants and the many cucurbits, which include melons, summer squashes and cucumbers, plus snapbeans and sweet potatoes. Frost-tolerant vegetables often originated in northern or temperate climates. These include the various cruciferous vegetables, which include broccoli, kohlrabi and cauliflower; cole crops like beets, Swiss chard, kale, cabbage and spinach: and root vegetables, such as carrots, beets, radishes, parsnips, and turnips.
When a sudden temperature decline is forecast, growers first should protect the most sensitive frost tender crops. Damage usually occurs in these crops when temperatures dip into the low 30s and 40s. To do this:
– Water the soil around the plants. Wet soil holds more heat than dry soil and this retained heat will be released when the air temperature around the plant is less than the soil temperature. This is particularly effective in elevating soil temperatures when the day is sunny and warm before an overnight temperature dip. Well-watered plants are less susceptible to chilling injury.
– Use row covers to hold heat around the crop plants. Row covers can be made from many materials, such as old bed sheets, newspapers, old sheer curtains, or purchased lightweight non-woven polyester. Places on the plants where the row cover touches may have frost damage. Support stakes or wires can be used to support the cover and edges should be secured to the ground to reduce heat leakage and wind damage.
– The openings for the plants planted in black plastic mulch act as chimneys allowing soil and air heat under the mulch to escape, providing some additional warmth in the crown area of the plants. Although some of this heated air will be captured by the plant canopy, use of row covers will provide additional protection.
Frost-tolerant vegetables are the delight of the fall garden, often providing fresh vegetables until late November. These crops are generally tolerant of temporary temperature dips or night temperatures into the upper 20s and 30s. While using the protective measures described for tender vegetables will be beneficial, many can withstand their leaves freezing during the night.
Don't try to harvest frozen or frosted leafy greens (lettuce, chard, etc.) or try to thaw the leaves by sprinkling with water. Frozen cells will burst with the sudden change. Continued harvests depend on the leaves thawing gradually as the air temperature slowly rises during the morning hours. Harvest more mature leaves a leaf or two at a time, leaving the smaller leaves protected for continued growth. Just before the final killing frost, harvest the entire top but leave the roots and the apical center of growth. By leaving the plants to over-winter in the ground, perhaps with a covering of mulch, you may be rewarded with an early harvest of spring greens.
Cultivars differ in their adaptability and each year weather conditions are different so your own experience is the best guide. Spinach, kale, collards, and Swiss chard are most adapted to over-wintering in Nebraska.
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http://ianrnews.unl.edu/static/0908250.shtml
Source: Laurie Hodges, (402) 472-1639
Editor: Dan Moser, (402) 472-3007
