Don Riddle, an enterprising nurseryman who made Homestead Gardens in Davidsonville one of the leading garden centers in the United States, died June 30.

Mr. Riddle, 63, was found hanging in the 42-foot powerboat he kept docked at his home in the bayside community of Annapolis Roads.

His death, ruled a suicide by the Maryland medical examiner’s office, sent a shock wave through the plant nursery industry, whose members traveled from across the country to attend his funeral July 7 at St. Anne’s Episcopal Church in Annapolis.

Mr. Riddle’s son, Brian, said his father had recently been battling depression, in part because of the effects of the recession. “Dad was under tremendous pressure the past couple of years,” he said.

Don Riddle founded Homestead Gardens in 1973 and then developed it as a destination garden center on a prominent 65-acre site at the Davidsonville crossroads in Anne Arundel County.

With its broad array of perfectly grown plants under attractive pavilions, skilled staff, and seasonal attractions, it was widely regarded as a model of how independent garden centers could survive and flourish in an era of cutthroat competition from mass merchandisers.

Over the years, as Mr. Riddle expanded his enterprises to include a landscape construction company, a wholesale nursery and an enclosed five-acre production greenhouse, he also became actively involved in the cause of garden centers nationally.

He made Homestead a member of a national network of top independent garden centers and served on the six-member board of the trade group Garden Centers of America. He was also vice chairman of the American Horticultural Society.

As part of several civic activities in Annapolis, he took charge of the historic district’s beautification efforts, and he also maintained the flower displays at Camden Yards in Baltimore.

“He had a real knack for understanding what his business needed to do,” said Katy Moss Warner, president emeritus of the American Horticultural Society. During the past five years, when the “big craze came” for growing your own vegetables, Warner said, “he got on the tractor and started growing and selling vegetables. He had a sense of urgency.”

The company has 350 employees at its seasonal peak with annual receipts of approximately $25 million, most of it at the flagship garden center. A second retail nursery opened last year in Severna Park.

From the start, Mr. Riddle kept his business open much of the year — rejecting the standard business model of the retail nursery that does virtually all of its business in an eight-week period between mid-April and mid-June.

At Homestead, he insisted on the latest plant varieties and having a knowledgeable staff. He added such extras as barbecues, a paddock of llamas (better to create a “destination” to families, he said), gardening demonstrations and elaborate seasonal events, including an autumn harvest festival. The nursery parking lot was landscaped with lavish display gardens.

At year’s end, he wanted a holiday and Christmas display experience akin to the ones that drew Macy’s customers in New York in the 1940s, said Tim Hamilton, Homestead’s marketing director.

Mr. Riddle sent buyers and senior staff to trade shows and premium garden centers across the United States and in Europe. A pivotal moment came in the early 1990s when he studied what the Walt Disney Co. was doing in Florida.

“He came back with two words: ‘everything speaks’ — trash on the ground, doorknobs with dents, tables with rust on them,” Hamilton said. “Everything adds up to the sum of your experience. He wanted an experience, not a shopping trip.”

Associates said he made a point of sharing his expertise with other garden centers, and he instructed his senior staff “that if a garden center called in need, you’re to give them the attention they required,” Hamilton said.

Don Eugene Riddle Jr. was born in Cheverly on March 24, 1948, and grew up in Hyattsville. After graduating in 1966 from Northwestern High School, he served in the Navy before attending the University of Maryland to study horticulture. Impatient to start a nursery, he left in his junior year and started a business from his parents’ home.

His first marriage, to Jenny Cronin, ended in divorce. Two daughters from that marriage, Emily and Sharyl, died in infancy.

In addition to Brian, a son from his first marriage who lives in Flemington, N.J., Mr. Riddle’s survivors include his wife of 16 years, the former Laura Kroto, and their daughter, Quinn, both of Annapolis; his mother, Evelyn Riddle of Hyattsville; a brother; and two grandsons.

Adrian Higgins is the gardening columnist for The Washington Post.