Gardening grows on you. That’s one reason so many people discover the hobby later in life.

Baby boomers are gravitating toward gardening as a way to exercise, unwind and spend time together. It’s one of a number of trends that converged in backyards across America last summer as more than 7 million families planted vegetable gardens for the first time, according to the National Gardening Association and other experts.

Those newbies fueled a major boom for Burpee, the go-to seed source for generations.

“It’s been a wonderful two years for us,” Burpee owner George Ball says from his Pennsylvania headquarters. “We were at the right place at the right time. So many trends came together at once. It was a perfect storm for vegetable gardening.”

Burpee saw its sales go up 20 percent to 25 percent in 2008 and again in 2009 – the biggest surge for the 134-year-old company since 1973, itself a recession year.

Spurred by the economic downturn, many American families returned to gardening or tried it for the first time as a way to save money. Growing one’s own food also is a way to ensure its safety, another major concern.

“But there’s this big background trend behind all that now,” says Ball, 57, an avid gardener. “We’re getting older. We have more time. We may finally have a home of our own and a backyard. We have space. We want to garden. That trend will continue even as the economy improves.”

Last month, Burpee mailed out almost 1.8 million copies of its signature catalog. About 600,000 catalogs under its other nameplates will be delivered soon.

As always in its catalogs, Burpee trumpets what’s new and unusual.

“We scour the world looking for them,” Ball says. “We’re always trying to push the envelope. It’s not the same old seeds we offered 30 years ago.”

Burpee keeps fresh every winter with a plethora of eye-popping, never-seen vegetables and flowers. Those new introductions – such as Tie-Dye Tomatoes and RSVPeas – take five to six years to develop as hybrids. Some fruit trees take decades before they reach the catalog, which has 75 new introductions for 2010.

“Gardeners want to know what’s new,” Ball says. “They want all that sweat to pay off every year with something they can’t find anywhere else. It’s a really big deal. It’s hard to find something exciting every single year.”

Ball understands what gardeners want. For decades, the Burpee owner has seen fads come and go, but his brand has remained supreme.

The main Burpee catalog is supplemented by two niche catalogs: The Cook’s Garden for gourmet veggies and Heronswood for rare perennials and weird plants.

“We’re an old company,” Ball says, “but we’re actually the youngest company at heart.”

He has kept his company in step with modern trends while keeping the Burpee name synonymous with vegetable seed. It has the country’s top catalog and sells seeds in home-improvement stores.

The most popular sellers are the standards: zucchini, sunflowers and zinnias.

“They’re easy” for gardeners, Ball says.

Judging by early sales, Ball expects another great year for Burpee.

“This boom will continue for now,” he says. “But there will be some fallout (eventually). I can’t make people gardeners.”

Gardening is not for everyone, he acknowledges. Many people try it and give up, frustrated by lack of success after all that work. Keeping a large vegetable garden also is a major responsibility, like owning a horse.

“You have to be able to put up with dirt and bugs,” Ball says. “You’re going to sweat. But if you survive a year and want to plant again, then you know. You’re a gardener, and you’ll probably stick with it for life.”