Spring is make-or-break time for garden centers, and Mollie Plotkin is doing her part.

Plotkin's designed and planted her first vegetable and herb garden. She's gone completely organic. She's canceled her landscaping contract and bought an electric lawn mower. And she's trading splashy, one-season annuals for long-lasting perennials.

They may be buying less, and they're certainly buying smarter. But plant-lovers are still spending, which means that even in this recession, garden centers - with some notable exceptions - seem to be doing OK.

"I've been doing this for 37 years and been through some significant stuff, but I honestly didn't expect business to be as strong as it is," said David Green, third-generation president of Primex Garden Center in Glenside, which does 60 percent of its business from March through June.

Perhaps it's not so surprising.

Trees and flowers are a $10 billion industry in Pennsylvania alone, second only to dairy and beef, and consumer spending on lawns and gardens nationwide - now more than $36 billion a year - has been growing since 2006.

Plotkin and her husband, Kevin, who works for a finance company, are typical of the customers that Primex and other garden centers are seeing this atypical spring. They're doing it all themselves, but they're buying.

"We'll be spending a lot more time at home this summer," Plotkin said. "We can do this."

Plotkin read up on do-it-yourself gardening at the - free - Radnor Memorial Library. She designed and planted a large bed for vegetables and herbs and a smaller perennial plot that she'll enrich with homemade compost.

In a trend fueled in part by the economy, the National Gardening Association estimates that seven million more Americans will plant vegetable gardens this year, an increase of 19 percent over 2008.

Plotkin, whose sports-marketing business has dwindled significantly in the recession, used to spend $200 a year on annuals like impatiens. On Thursday, she spent that amount solely on salvias and other perennials at Waterloo Gardens in Devon. She bought plants that last.

And for the first time, she paid cash. "Usually I do a credit card, but this way, I have restraint," Plotkin said.

Her strategy is being replicated across the country, according to Mark Delaney, who studies home-improvement trends for the NPD Group, a marketing-research firm in Port Washington, N.Y.

In a recent survey, Delaney said, 41 percent of consumers said they expected to cancel or change summer vacation plans. "From where I sit . . . that says to me, OK, I'm going to be spending more time around my house and probably spending more on the outside of my house," he said.

Lawn and garden products are considered a "feel-good category," Delaney explained. "So when I pull up the driveway at end of the day, or I go outside with a cool drink on Saturday night, or invite my friends over and fire up the grill instead of going out for dinner, I want the place to be reasonably attractive."

Jim Feeney, who founded Feeney's Nursery & Garden Center in Feasterville in 1962, is counting on the stay-at-home trend to keep sales steady, along with some adaptations.

Big-box stores have made huge inroads selling cheaper plants and products, forcing garden centers like Feeney's to add expensive grills and outdoor furniture and nongarden items like baby clothes and women's hats.

"So even if we don't sell people nursery stock, they come back three or four times a year for gifts," said Feeney, president of the 450-member Garden Centers of America.

Although business has dropped slightly in the last two years, Feeney's customer count this spring is up 10 percent, even as the average purchase has dipped from $60 to $50. That's hard to believe, considering sales of vegetable and herb seedlings are up 250 percent when compared with last year - and $20 "Whopper" tomato plants and $50 pre-planted flowerpots are big sellers.

One day last week, Susan Kinney of Feasterville was loading up on tomato and pepper seedlings. "I make a lot of spaghetti gravies for my husband and three boys that we freeze and eat all winter," she said. "We're trying to save where we can."

Waterloo Gardens, another third-generation family business, also is seeing more customers and lower average purchases, although in this case, a scaled-down buy might be a $3,000 patio set instead of one for $10,000 or even $20,000.

"It's not every day somebody comes and spends that, but some people have large patios," said Mark Rosenthal, general merchandise manager and marketing director for Waterloo, which has stores in Devon, Exton, and Wilmington.

In fall 2007, just as the economy was slipping into recession, Waterloo opened a fourth store in a converted Pathmark supermarket in Warminster. It closed after Christmas last year.

"I think Warminster was bad timing," Rosenthal said.

Rich Flagg, president of Flagg's Garden Center & Nursery in Moorestown, takes the long view. While his landscaping and carpentry jobs are down, flower sales are up; that's just how it is.

"Throughout our history, we've seen that. In poor economic times, we seem to do a little bit better with those things," said Flagg, whose parents started the business in 1955. "Everybody can afford to buy a hanging basket or a flat of annuals, and it goes a long way psychologically."

Another factor lending staying power to garden centers is that they tend to be on the fiscally conservative side. "So they don't boom as much when the economy booms and they don't contract as much when the economy is contracting," said Jonathan Bardzik, marketing director for the American Nursery and Landscape Association.

For all the talk of economy, for many garden centers, weather is a bigger worry long-term. "After all," said Green, of Primex Garden Center, "spring comes once, that's it, and rain can be very expensive."

Contact staff writer Virginia A. Smith at 215-854-5720 or vsmith@phillynews.com.