One of the best ways to keep our environment healthy is to use the safest and soundest methods of gardening and weed control, such as conditioning the soil, mulching plants, hand-weeding and doing all we can to protect the planet's existing plants.

Soil is as important as sunshine for the health of your plants. It's their growing medium, the source of nutrients, an anchor for their roots. It dictates drainage and structure so plants can absorb air and moisture. Understanding soil and learning what it needs to keep plants healthy is critical to establishing and caring for them, especially through the stressful periods of their life, such as harsh winters and summer drought.

Soil is composed of very fine particles of weathered rocks. Plants and animals add organic materials to this through decomposition or the decay of their waste and other byproducts. The minerals and decayed organic materials together create topsoil.

It takes Mother Nature hundreds of years to do this. In the past century, though, we have stripped or robbed most of her work by removing trees and skimming the topsoil to make room for highways, housing developments and industrial parks. And we aren't replacing it.

When I studied at the University of Maryland, we tested area soils. At times we found only 1 to 2 percent organic material from Maryland and Virginia farmland. A good planting medium should have 20 to 30 percent organic content. It's what keeps the plants happy and healthy. So unless you have a forest floor that has been undisturbed for many years, you need to add composted organic material.

Preparing a site before planting ensures success. And you only get one chance before the plants go into the ground. You never get the opportunity again to reach a plant's root zone so easily.

In early spring, after the soil is no longer soggy, dig a two- to three-inch layer of nutrients into the top 10 to 12 inches. I've seen the positive results of plant vitamins, humic acid, kelp and fish byproducts. Even when a soil test reads "no nutrients needed," products such as Vita Planta, BioPlex, Neptune's Harvest Seaweed Plant Food, Roots and Superthrive, to name a few, will stimulate a plant to survive and thrive in times of stress. They can be used in conjunction with fertilizers. Follow labeled instructions.

Another way to enhance soil is to use compost as a mulch. Spread a two-inch layer over beds. Soak it in, and let gravity go to work. Mulch holds moisture, helps control weeds and can make a tremendous difference in plant health in just one growing season. Composted yard waste can be used, as well as other composted organic material from your garden center (or look in the Yellow Pages under "mulches"). To control weeds, I prefer organic, partially composted materials rather than herbicides. Compost is a practical weed control. Other materials that can mulch out weeds are straw, salt hay, ground corn cobs, pine bark nuggets, cocoa bean hulls, shredded hardwood bark, licorice root, wood chips, newspaper, landscape fabric, stone and even shredded tires. Don't pile mulch against the bark of trees or shrubs.

Protecting the existing flora is one of the best things we can do for the environment. It takes about a decade to create the perfect mix of trees, shrubs and perennials for a landscape. And impatience (not the flowering kind) or indifference are the reasons many landscape designs don't reach their greatness. Great landscapes are those that will thrive for generations with only minor alterations.

Here are some tips for creating hardwood environments that will be hospitable to mature trees:

* Don't stake or wire trees into place unless necessary. Research shows that they establish better if their tops are allowed to blow in the wind without being staked and wired. It's only necessary to stake and wire newly planted trees with bare roots or a broken ball that might blow over in a storm. With a good root ball, it's usually not necessary. The greatest problem with staking is that there is seldom a plan to remove the stakes and wires. The tree grows around the wire; it impedes normal flow of nutrients, and the plants often die. Always remove guy wires in one year. If you must stake trees, use tree stakes from a garden center. Wire the tree on three sides to keep it from blowing to one side or the other. Use rubber hose to protect the bark from the wire.

* Bonnie Lee Appleton, a nursery and landscape extension specialist at Virginia Tech, says: "Remember, you're not 'feeding' the trees. They don't go chomp, chomp, chomp. You put down raw materials, and trees use these items to feed themselves."

Contrary to what was once thought and widely advertised, it's not plant "food." There is no need to deep-root-feed by injecting the fertilizer deep into the earth. Most root activity is in the top four to eight inches. It's also ludicrous to fertilize when the soil is dry. Moisture is crucial; the tree can't use one granule of fertilizer without it.

Apply fertilizer when plants are actively growing, not in late fall or winter, but in spring as buds swell and in late summer for fall root growth. Nitrogen has been found to have the greatest impact on tree growth. But too much will cause excessive, unhealthy growth. All elements should be balanced. As a general rule, don't fertilize trees growing in wooded, natural areas or in fertilized turf. However, growth stimulants, such as Vita Planta or one of the others listed above, have been used in natural forests to help combat stressed conditions that can lead to insect and disease problems.

* Avoid damage with mowers and string trimmers, which can shorten the life of a plant.

* Never use lawn weed killer over the roots of trees, shrubs, perennials or annuals.

* Don't use pruning paint over the cut of a tree. It can hold moisture and offer a habitat for organisms to invade the tree.

* Let fallen leaves at the base of trees decompose to provide the basis for a nutrient-rich compost for their roots.

* One final tip comes from biblical scholar Johanan ben Zakkai, circa 70 A.D.: "If a man is planting a tree, and someone comes to him and says the Messiah has come, let him finish planting the tree and then meet the Messiah." Since tree planting is considered such a significant occurrence, we should practice what's preached.

For information about responsible plant design, call the Alliance for the Chesapeake Bay, Chesapeake Regional Information Service, 410-377-6270; Web site: www.alliancechesbay.org.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. His e-mail address is jml@gardenlerner.com; his Web page is at www.gardenlerner.com.