Each day Margaret Richert looked out the window of her Annandale home and saw that the spots on her lawn were growing larger. The professional home lawn care company she was then using told her the problem lay with cinch bugs, a common garden pest. A spokesman said they would be right over to kill the beasts.

But the company never came, even after repeated calls, and two months later her lawn was dead. "The chinch bugs ate it," she said ruefully.

Undaunted, she retained another professional home lawn care company, which reseeded the ground and now maintains if for a $500 annual fee.

"We have a stand of grass you wouldn't believe. It makes you Proud to look at it," she said.

The anecodote illustrates the dangers and benefits of an industry that just a few years ago was best represented by a bunch of men with lawn mowers hanging out of the backs of station wagons.

Today it is a $750 million business, with a 25 percent annual growth rate, relying on electric equipment to test soils and university experts to analyze it. Some companies require agronomy degrees of the workers they hire. Others claim they train them on the job.

Industry spokesmen say only about 5 percent of U.S. lawns are currently cared for professionally, and quote a recent survey showing that anything beyond a single application of fertilizer adds $1,400 to the value of a $50,000 home.

"People don't have the time to take care of their lawns, or they get discouraged when they spend a lot time in the yard and don't see an improvement," said Joe Stout, president of Complete Lawn Service, Inc., the firm that rescued the Richert lawn from a fate worse than slugs.

Like many companies in the field, Stout's firm employs about a dozen people, has about 100 customers, and cares for a lawn on a year-round basis.

For a fee that often starts at about $125 annually, but can grow like Topsy, companies like Stout's will seed, feed, fertilize, or debug a lawn. Some of them will even dye it, if that's what the owner wants.

"A lawn to a homeowner is like lipstick to a woman," said Anthony Giordano, president of the New Jersey-based Lawn Doctor company, which grossed $10 million in the sale of franchises and supplies last year. "People want their lawns to look good so their neighbors will see it. I've written $350 contracts in living rooms that didn't even have furniture - people would rather have a good lawn than a couch." he said.

Giordano started out pushing a lawn mower himself, then later moved to the front office, a typical story in an industry in which many of the 4,650 companies gross less than $100,000 annually.

"People would call me up and say, 'Lawn doctor, I've got a pain in my grass.' So I'd give them a prescription: "Take some pre-emergent crab grass killer, or some balanced fertilizer, and call me in a few weeks'," he recalled.

The standard pitch in the industry is that because companies can purchase chemicals at cheap bulk rates, a homeowner will pay only slightly more for a company to care for his lawn than he would if he purchased and applied the chemicals himself.

"We do not sell a product, we sell a service," said William N. Vorn Holt, a vice president of Ohio-based Chem Lawn, the largest company in the field. Chem Lawn last year grossed $52 million from work on 350,000 lawns, with an average annual fee of $134 for the typical 8,000-square-foot East Coast lawn.

"A woman once called me on Christmas Day when her lawn was under four feet of snow and asked me to check on it," Vorn Holt said. "She was worried about it." He declined the invitation.

There are two types of companies in the field: those that spread chemicals in liquid form on lawns, and those that spread chemicals in pellet form.

Charles H. Darrah III, an agronomist with the University of Maryland, a consultant to the industry, explained that liquid chemicals can produce improvements faster on lawns, although there is the risk of a chemical burn if the proportions are not correct. Granular chemicals produce results more slowly.

The local industry generally offers March-through-December lawn care in the Washington metropolitan area, one of the most difficult in which to grow grass because of climate and soil variation, Darrah said.

Depending upon what a lawn needs, a company might spread fertilizers, herbicides, insecticides, or fungicides. If reseeding is necessary, a company might choose either rye grass, or more usually, one of the 65 different varieties of Kentury blue grass available. If a fungicide is needed, it must be specific for whichever of 1,600 types of fungus are gnawing at the roots of the lawns.

The soil itself might be aerated, or "dethatched," which is basically clearing away accumulated layers of dead organic material.

"A neighbor called me to wonder about the man who was always digging in my back yard," one woman said. "I told her it was only the lawn man." The woman does not want her name published because she is afraid neighbors will try to "steal" her lawn man from her.

Every professional has his favorite story of tricks played by his competitors, such as reseeding a lawn when it isn't necessary, selling a combination of broken straw and seed as "topsoil" or billing the customer for chemicals that are never spread on his lawn.

Another trick, often played in conjunction with new home builders, is to seed a lawn in early spring with quick-growing rye grass in order to meet the requirements of many local jurisdictions that a lawn be in place before the house can be sold.

"But if the rye grass is not tended properly, it will die in the summer time, which often happens when people don't know anything about lawns, or are too busy moving in," Charles Darrah said.

"The most important thing we've done recently is clean up our act," said Robert Earley, editor of the trade publication, "Lawn Care Industry," and an unofficial industry spokesman. "We've gotten rid of the guys with a lawn mower who went door to door and didn't know anything. We've professionalized, conducted our own research, made contact with the universities and land grant colleges. Interest is high," he said.

"We really don't know what they (members of the industy) are doing, although we haven't had any problem with them," said Robert C. Rund' a Purdue University professor who is secretary of the Association of American Plant Food Control Officials, a national group of state and federal experts.

"Since they're selling a service, there are no real regulations over the stuff they sell along with it. But how good the fertilizers they use? Are they really putting down the amounts they say they are? Is the customer getting what he's paying for?" Rund wondered.

There are currently no appliable federal laws regarding the industry, except those regulating the use of pesticides, for which licensing is necessary, Rund said

Several franchise lawn companies have had bankruptcy problems recently, and a few have formally been charged with shoddy dealings. Locally, however, the Better Business Bureau and other responsible agencies report no complaints about the lawn care companies.

"If you don't do anything you'll have a lawn, that's nature's way," said Darrah philosophically. "You can have a good lawn by doing it yourself, if you follow directions on packages, or call your local county extension agent for help when you need it. That's what the lawn companies do," he said.