In ancient Egypt, physicians prescribed walks in the garden for disturbed patients. Patients planted and harvested crops in 18th-century mental institutions.

High-pressured executives today unwind by puttering in the yard or by re-potting houseplants.

"Caring for plants," says horticulturist Charles Lewis, "involves an incredible curative power. Particularly for people under stress, re-establishing that inner link with nature can be a marvelous therapeutic tool."

This little-studied "people-plant" connection is at the root of a new form of therapy -- "horticulture therapy" -- being used across the country to help handicapped, elderly, disabled and disturbed people capture, or renew, faith in themselves through the renewal of nature.

"Working with plants helps people get in touch with the reality of their environment," says Earl Copus Jr., director of the Melwood Horticultural Training Center in Upper Malboro. "That's the first step on the road to functioning in society."

Melwood, a 1963 pioneer in horticulture therapy, was started by parents and friends of mentally retarded adults on six acres of government surplus land.

"At that time, the basic job opportunity for retarded adults was doing tasks like stuffing envelopes or twisting two wires together all day," says Copus, 43, a former Peace Corps volunteer with a degree in forest management. "These parents wanted another option."

From six students and one instructor, Melwood has grown to serve 200 "trainees" at the center and on their 100-acre farm in Charles County. Staff members are trained in a variety of skills, including psychology, botany marketing and food service.

When the Melwood success story attracted a flood of interest in the program, Copus in 1973 organized the National Council for Therapy and Rehabilitation Through Horticulture.

Today the council has 850 institutional and individual members; nine universities offer degrees in the field, and dozens offer plant-oriented courses in occupational-therapy or recreation curricula. More than 500 jobs were available last year in the field, says NCTRTH. Applications are expanding, from greenhouses attached to nursing homes to urban gardens projects.

"The benefits involved in horticulture therapy," says Copus, "are varied. First there's the value society places on plants, which is transferred to the individual who tends the plants. There can be a lot more satisfaction in growing a nice plant than putting a washer on a bolt.

"People are also willing to pay money for plants, which makes horticulture a way to earn a living. (Forty percent of Melwood's budget comes from sales of its plants and landscaping services.) It's also a good way to teach someone vocational skills they can apply to other jobs.

"And it's a good way to integrate special populations -- like the elderly or mentally retarded -- into the community. When our people go out to do grounds maintenance at a place like RFK stadium, it gives the community a chance to appreciate what they can do."

A more subtle value is the built-in dependency plants have on people.

"Everyone needs to feel needed, says Copus. "A living plant needs and depends on you. It doesn't care if you're disabled. Knowing that a plant relies on your care can give you a reason to get up in the morning."

Plants also have a calming influence, contends Copus, who takes a 15-minute "greenhouse break" for relaxation from administrative duties. "It provides a real release valve from the pressures of our highly-intense society.

"I think there's a psychological -- or perhaps biological -- link between people and plants that goes back to creation. Since the time we rooted around in the soil for our food we've enjoyed having greenery around. Which may explain why there's been an emphasis recently on having plants in the home and office."

Because John Deere & Co. management believes plants in the work environment help morale, productivity and customer relations, its headquarters in Moline, Ill., are lush with greenery.

Centered around an indoor garden the size of four tennis courts, the office is designed so that "no worker is more than 45 feet from the vegetation," says Deere spokesman Robert Shoup. "It creates a very relaxed, yet stimulating environment. We have very little turnover at this company."

The interplay between plants and people "is just beginning to be studied," says horticulturist Lewis, who does "plant/people research" with the American Horticultural Society.

"We sent out a questionnare to members asking what satisfied them most about gardening. The major responses -- more than winning prizes or growing pretty flowers -- were the feelings of peacefulness, quiet and tranquility that came from working with plants."

Part of this peacefulness comes from "the natural order observed in the plant world," says Lewis. "You can eagerly await a seed's growth, watch it mature, harvest fruit or enjoy flowers and deal with its death.

"It can be a symbol of order in a chaotic world, a sign of life in stagnating social systems. You've got to look beyond the pretty flowers to see the real connection.

"When someone grows a plant, you get more than a beautiful plant. You get a beautiful person."