When Leon Seidman left the University of Maryland in 1977 to grow catnip in the rural countryside near Hagerstown, he was a long-haired graduate student who "couldn't really set up with playing the campus political game." So he opted instead "to live on a farm where I wouldn't have to worry about all that . . . where I wouldn't have to worry about the rush-hour traffic on University Boulevard."

Today he is said to be the country's largest catnip producer, turning out 25,000 pounds of the feline wacky weed each year on 40 acres of prime Maryland farm land. Under the Cosmic Catnip brand name (Seidman's own) and a myriad of other labels, he markets his product in about 120 stores and chains across the nation, including K-Mart.

Starting this spring, Seidman's $400,000 annual business will get a boost when his catnip hits the shelves under the Sergeant's label--an initial order of 50,000 half-ounce bags.

Admittedly a novice when he started ("I knew nothing about business . . . about organization or how much time it took"), the former American history student and anti-Vietnam War activist plunged into the catnip game six years ago because he was convinced that an untapped market existed for a quality product.

He'd started growing catnip in his Langley Park back yard in the early 1970s because his three cats turned up their noses at the inferior stuff he was bringing home from area stores. Given a decent product, Seidman said, most cats will eat catnip two or three times a week, often rolling in it and otherwise demonstrating their ecstasy.

And sure enough, the cats liked his homegrown variety so much that he was soon running a part-time business selling it to local pet stores.

"People started calling me asking me where to get it," Seidman recalled. The only major problem was that enterprising teen-agers were buying it up from some retailers, repackaging it and selling it as marijuana. Although catnip doesn't have the same effect on humans as marijuana does, he said, it can be used to make a bitter tea that's effective against upset stomachs.

Torn between devoting himself to a master's thesis on the history of the nude in American society or the full-time culture of catnip, Seidman recruited three other growers (one, Phil Gamerman, remains a partner), moved to western Maryland, and began raising the plants for market.

It proved to be no easy task. Seidman's first bulk purchase of catnip seed turned out to be something else entirely; eventually he had to learn to grow his own seed. Germination of the hard-to-domesticate plant occurs at a rate of only about 28 percent; the crop has to be rotated to avoid buildup of a naturally occurring fungus. Despite all precautions, Seidman lost nearly a quarter of his crop to fungus during a drought last spring.

Weeding is tricky because catnip, itself a weed, is killed by herbcides. Seidman is now experimenting with Chinese geese to ease the agony of hand-pulling.

"Geese are used to weed mint and tobacco fields, and they don't like catnip," Seidman explained. "They'll eat thistles before they'll eat catnip. They walk up and down in lines; they weed and fertilize as they go."

In the early years, Seidman and the fledgling business underwent many changes, in style as well as substance: The former long-hair said his hair got shorter as he became more involved in the business.

Trying to convince buyers there really was such a thing as quality catnip, he traveled at first to about 75 cat shows a year--more than one a week.

"One of the things that's happened since I came along," he said, "is that the quality of catnip on the market in general has increased, because other manufacturers have to compete with me." At first, many commercial catnips were so old, or contained so much stalk and so little leaf, that "what was being sold was garbage," he maintains.

But while his sales pitch gleaned him a share of the market, it also proved such a time drain that it contributed to the breakup of his first marriage, Seidman said, and eventually he decided that "I really wanted to be a manufacturer and a farmer."

After the first year, Seidman's partners dropped out, largely, he said, "because none of us knew anything and everyone was a complete ego." Even Phil Gamerman, his current partner, left for a time. "Phil wanted to be a massage therapist down in D.C.; he didn't want to be a catnip farmer. I had hustled him into it."

But several years later Gamerman returned. The two men restructured the business into what it is today, selling the pet-show portion to another partner, and Gamerman began designing and building virtually all the equipment that chops, sifts and sorts the catnip.

Today, Seidman lives on the 117-acre farm in Leitersburg with his second wife and their four children. He travels very little and spends 80 percent of his time during the growing season in the fields. Sales are handled by three commissioned salesmen; nine other employes work on the farm and in the 5,500-square-foot warehouse in Hagerstown where the sorting and packaging are done.

"Last year was the first time the business made any money," Seidman said. "And this year . . . it should become what we call seriously successful."

Aside from catnip, the company now sells pet toys and two deodorants, one for kitty litter, the other an all-purpose household deodorant that Seidman and Gamerman devised and "that should soon become a major market items." There is also an innovative mix of kitty herbs--seeds to be planted and, after sprouting, fed to housebound cats. "It keeps them away from the houseplants and gives them chlorine and fresh vegetable matter they need in their diet," Seidman said.

Other, unprofitable items have recently been dropped, largely because "last year was the first time I felt I had any sense about business . . . that I understood cost anaylsis and profit margins," Seidman noted. "It took six years to grow."

And yet behind the successful entrepreneur remains a trace of the anti-war activist, even today.

"I'm at the point that I can even think about suing somebody if they don't pay. It's frightening. I don't know where you're coming from personally, but to me . . . I still consider suing a violent act."