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Two weeks ago we discussed some of the ways Mother Nature damages our plants during the cold weather. If you have not yet protected your trees from winter injury, you can still do that by wrapping the tree with a white tree wrap or painting the barks with 50 percent exterior latex paint. You can also still mulch your plants to protect them. We also emphasized that the most important thing is to select only those plants that are adapted to our intermountain growing conditions.

It's very important to keep your plants as healthy as possible. Strong healthy plants are able to overcome freezing stresses much better than plants that have suffered insect or disease damage, water stress or nutrient deficiencies. Plant acclimation is an active process; that is, the plant must be healthy and actively growing to acclimate to our cold winter temperatures. We can often assist the plant to harden off by avoiding soluble plant fertilizers in late summer and by reducing or eliminating our fall irrigations to slow plant growth. Likewise we should not be in a hurry to prune in the fall. Even after leaves have dropped, pruning can stimulate some cell activity and result in a loss of hardiness. Wait until 1990 to begin any of your dormant pruning.In addition to keeping plants healthy, it is important to minimize frost heaving. The alternate freezing and thawing of soil has tremendous impacts upon the soil structure and aggregation. There are some beneficial aspects of freezing and thawing in clay soils, but rapid freezing will tear the roots from the plant and damage it severely. Water actually expands about 10 percent in volume when it freezes. This freezing and thawing will cause the soil to heave or lift up, which may force shallow-rooted plants out of the ground or tear the roots from more deeply rooted ones. This type of freezing will damage perennials, roses, newly planted lawns and winter annuals and biennials.

The best prevention for this kind of damage is a good snow cover. Snow is an excellent insulator and also prevents drying. Since we have no control over the snowfall, we substitute mulches. Anything that serves as a good insulator, including leaves, straw or wood shavings, will work, providing they do not pack down. Styrofoam containers that cover the entire plant are also available. As mentioned previously, the function of mulches is to keep the plant and soil cold, not warm. Soil that remains frozen will not damage the plants as the freeze-thaw cycle does. Organic matter also helps hold the soil together, further lessening the damage.

Another important thing is to reduce winter desiccation. Desiccation results when plants lose water faster than they take it in through the roots. During the winter when soils are frozen, little or no water can be taken up through the root system of most plants. The above-ground portion of the plant continues to lose moisture due to exposure to wind and cold, dry air.

Evergreen plants are very sensitive because they continue to lose the greatest amounts of water through their needles or leaves during the winter. Broad-leaved evergreens use more moisture than needle-type evergreens, but both can be damaged. Unfortunately, our weather pattern for the past three years has made plants very susceptible to damage. Long, hot, windy summers followed by warm, dry autumns mean there has been very little moisture available to the plants. Recent snowstorms have helped some, but winters have generally been cold and dry, and this pattern causes severe damage to our plants. Euonymous, laurels and photina and other broad-leaved evergreens, because of their high water use, are particularly sensitive, but damage has also been severe on pines, spruces and firs.

If only the leaves dry out, the plants will recover, but in many cases the plant will die. This damage is reduced by careful watering. Do not overwater your plants during the growing season and make sure your plants have a good soaking before the soil freezes. Plants under the eaves of buildings are not watered because they miss the natural precipitation. These areas are warmer, so more water is lost from the soil by evaporation. Check soil moisture during the winter and water as needed. Usually one or two waterings during the winter will be sufficient. Avoid using broad-leaved evergreens on southern or western exposures. Plants on these exposures, near buildings or fences, are particularly sensitive.

Certain nursery products are sold to reduce losses from drying leaves. Wilt Pruf and other anti-transpirant products are examples. They may help some plants but are no substitute for selecting the right plant for the right location and giving that plant the care it needs.

In case you haven't selected all of your Christmas gifts, there is still time to make a visit to your local nursery, garden store or florist. Plants continue to be a very popular item for Christmas. If you select a plant, make sure you keep it warm as you transport it to the recipient. A living plant will provide enjoyment to a gardener throughout the coming year. Potting materials such as a bag of soil, ceramic pots, brass planters or other accessories to display that favorite plant will also be a welcome gift.

You may also consider one of the excellent garden books that are available on the market. Ortho, Sunset and HP Books all publish beautiful high-quality full color books on all aspects of gardening. These are available at most nurseries and would be welcomed by gardeners as they spend the long winter nights waiting to get out and work in the garden. Other more specialized books can be found at bookstores throughout the area.

Garden tools also make excellent gifts. Pruners, hoes, rakes, shovels would be a welcome addition although they may not be used for several months. Amaryllis, paper whites or other bulbs can also be purchased and forced.

If you ever have difficulty locating a particular variety of flower or vegetable, a certain tree or piece of garden equipment, call us on the KSL Greenhouse show Saturday morning from 7-10. This week we will try to help gardeners locate items they may not have been able to find as well as answer general garden questions. KSL is 1160 on your AM radio dial.

Merry Christmas to all of you!