It may not be spring yet, but trees can be planted any time now, if the ground isn't frozen and you can dig the holes. Bare-root trees are starting to come into the garden centers, and a bigger selection of trees will be available if you shop early.

Most trees don't grow well in heavy, poorly drained soils. Fill the hole you dig with water. If it doesn't drain away in 24 hours, think about changing location or modifying the soil and/or the terrain.Incorporate 3 to 4 inches of organic material into the soil to a depth of 10 to 12 inches. Rake enough of this converted blend into a berm with a 3- or 4-foot-wide, flat raised bed 6 to 8 inches above the original level. This should give you nearly 20 inches of loose soil that will drain well and in which trees or shrubs can be planted.

If you're in areas with high clay content, DO NOT add a lot of peat moss, compost or other organic material to the soil you put back around the roots. By changing that soil structure, you're inhibiting the water movement and potential root development. Those roots must grow out into the native, undisturbed soil as they enlarge, and that growth will be better encouraged without distinct differences in soil makeup.

There's an advantage to planting trees now - the roots will have a chance to get established. Then, by the time spring arrives and leaves appear, the trees' roots will be strong and more able to supply moisture and nutrients to the plants.

Select fruit trees wisely. They are an investment in time and money, and will be around for quite a number of years. And remember to buy fruit and nut trees that are recommended for our area. Also check to see if they require a pollinizer. Some are self-fruiting; others are not.

Fruits best adapted for backyard gardens include apples, sour cherries, peaches and nectarines. Pears are a little harder to shape up and get into production. And while sweet cherries and apricots are good, they are larger trees and are difficult to keep in small places. Other fruits that do well are plums - the Japanese varieties for fresh eating; the European for canning and drying.

Refer to the Feb. 8 column for additional information on fruit tree selection.

Fruit trees don't really double as shade trees because of their pruning, picking and spraying requirements. I'd suggest you consider nut trees if you want food and shade from the same plant. You pick nuts from the ground, not from the tree, so limiting size is not as much of a factor.

If you don't have a lot of space, almonds may be your choice. They're medium-sized trees that will survive where peaches grow. Nut production is better with two different varieties. Because the nut is a stone fruit, you'll need to treat for the peach tree borer each July and August to prevent trunk invasion.

In yards with more room, pecans or walnuts grow into magnificent shade trees. Experts suggest two trees be planted for maximum yield, but that requires a lot of space and single trees do produce some nuts.

I listed pecans first because they have fewer pest problems than walnuts. They're a handsome tree and somewhat unusual for our area. Having grown up in Arizona and knowing that in the Mesa heat nuts ripened in November, I was skeptical about their success in a cold climate. Mr. Richardson, in the Holladay area, showed me his flourishing, hardy pecan tree and shared mature nuts with me a few years back. He had planted a pair of trees, one of which had died. He still has a pecan crop, but has to battle the bluejays for his share!

Walnuts often are attacked by aphids. Their honeydew makes cars, picnic tables, toys, etc. unbearably sticky. In addition, a relatively recent pest, the walnut husk fly, invades the covering surrounding the nut itself. The meat is not affected but the nuts are rendered difficult to dry and shell properly. Amalathion application on Aug. 1 and 15 will pretty well control the pest if you know a way to spray a tree that size.

A more serious side effect is that the walnut husk fly attacks developing peaches in the neighborhood. Invaded fruit reveals maggots around the pit at harvest time. The same spray schedule is recommended for keeping peaches free of worms.

Ornamental shade trees are an important part of home landscaping. They'll provide cooling shade, summer and fall leaf color and enhanced property values. Decide what kind you need, locate them and plant as early as possible.

Trees that generate the most questions concerning their problems are white weeping birch, quaking aspen, poplars of various kinds, box elder and Siberian (Chinese) elm. Unless you have them in your yard already, consider these:

LARGE: Norway maple, horse chestnut, Norway spruce, Austrian pine. London plane tree, littleleaf linden, Japanese zelkova, catalpa, Japanese pagoda, hackberry, thornless honey locust and English oak.

MEDIUM: Red horse chestnut, golden rain, Bradford (or other callery pear), hornbeam, European mountain ash and hedge maple.

SMALL: Umbrella catalpa, hawthorn, Eastern red bud, amur maple, flowering fruit trees - crabapple, cherry, plum and Rocky Mountain maple.

This is not an all-inclusive list. USU publication EC406 describes and gives suggested uses for 100 "Ornamental and Shade Trees for Utah." Extension offices sell them for $7 but copies may be found in libraries and some nurseries as a reference work. One useful feature is the listing of campus locations in Salt Lake City, Provo, and Logan where you'll find various specimens.