At last, summer is sweeping over lawns. Once again, the grass is green and inviting. Perhaps you considered letting go of those 40-pound bags of chemical fertilizers and bottles of scary weed killers.

Let your grass out of its chemical prison so it can spread its roots in healthy, safe, full-of-life soil.

In the long run, you'll not only free yourself from worry about what lawn chemicals might do to your family and the world; you'll rid yourself of a lot of work.

"You don't need chemicals to take care of your lawn," says Rachel Rosenberg, executive director of the Safer Pest Control Project in Chicago (http://spcpweb.org) and former owner of a lawn-care service. "What you need is understanding."

Traditional lawn care — blanketing the lawn with standardized chemical treatments, squirting poison on any weed or disease that appears, cutting too short and watering too often — makes grass weak by ruining the soil it grows in.

Healthy soil is a rich sea of life, with billions of bacteria, fungi, single-celled protozoa, tiny wormlike nematodes, minuscule arthropods and other bustling organisms. As they consume organic matter, they release its nutrients to be absorbed by plants' roots. At the same time, they live in a boisterous but balanced competition that keeps any harmful organism from multiplying to the point where it can do harm. That's how plants evolved to live.

Water-soluble fertilizers deliver major nutrients such as nitrogen directly to the plants. That forces grass to grow fast — at the expense of creating thatch and starving the roots — and it destroys other life underground.

The soil becomes barren, with no way to fight disease and no source of nutrition other than your spreader.

Result? Feeble, stressed grass that is vulnerable to diseases and weeds. Many people respond by pouring on weed killers and fungicides, which slaughter more soil organisms.

So instead of treating the symptoms, fix the root problem by restoring your soil to let your grass live a normal life.

Here's how:

• Stop using chemical fertilizers and pesticides. Don't try to taper off, says Paul Tukey, founder of Safelawns.org, HGTV host and author of "The Organic Lawn Care Manual." Just quit.

• Add compost. A desert lawn needs a new settlement of bacteria, fungi, nematodes and other essential partners. It also needs plant matter for them to consume. So at least once a year, or ideally more often, spread a Z\x-inch layer of compost (either your own or ordered from a landscape supplier) over the lawn. After a few days it will work in.

• Mow high. Set the mower to 3 inches high. With more leaf area for photosynthesis, each grass plant will be able to generate more energy to send down deep, strong roots. The healthier plants will crowd out weeds, keep weed seeds from getting enough sun to germinate and keep moisture from evaporating as fast during the hot, dry months.

• Don't mow too often. Mow when grass needs it and not on a set schedule. Never cut off more than 1/3 of the grass blades at a time.

• Mulch clippings. Leaving clippings on the lawn returns the nitrogen they contain to the soil and feeds that underground population.

• Water wisely. If it doesn't rain an inch a week, give the grass a single long watering, not frequent sprinkles. Water that has time to soak in invites roots to grow down to find it. But if you sprinkle briefly several times a week, the water will stay at the surface. Shorter roots can't take up as many nutrients and can't reach deep water to survive dry spells.

• Use organic fertilizers. More are available today than ever before, even from major-label chemical companies such as Scott's Miracle-Gro. Organic fertilizers are designed to feed the soil organisms as well as the grass. They release nutrients slowly. Organic products do cost more, but their benefits pay off. Look for the OMRI seal (meaning the product has been reviewed by the Organic Materials Review Institute, www.omri.org).

• Aerate. Use an aerating tool or rent a machine once a year to remove plugs of soil, opening up the whole lawn community to water and needed oxygen.

• Choose a mix that matches your growing conditions (sun or shade). Rosenberg overseeds her lawn once a year, in early fall, by mixing grass seed with compost.

• Be patient. Grass won't green up instantly when you apply an organic fertilizer as it does when it gets the quick rush of a water-soluble chemical fertilizer. The green that eventually comes to a natural lawn will be a healthy green. It can take two or three years of organic care for a lawn to become thick and healthy.

• Chill. A naturally maintained lawn will not look like a golf green. There will be a weed here and there. Welcome clover, Tukey says, because it takes nitrogen from the air and adds it to the soil.