(FORTUNE Magazine) – If you've recently had an urge to manhandle a trowel or embark on a bout of mulching, you're not alone: Americans are expected to spend a record $38 billion this year on do-it-yourself lawn and gardening projects. Two-thirds of U.S. households will get in on the action, spending an average of $530 on everything from power mowers with air-conditioned cabs to potted petunias. (Small wonder that seed and plant catalogs flood mailboxes this time of year.)

The "nesting" trend may be partly responsible for the sales boost, says Bruce Butterfield, research director for the nonprofit National Gardening Association in Burlington, Vt. Not to mention the increasing number of baby-boomers with time--and money--on their hands. "I think people are genetically programmed to get into gardening as they get gray hair," says Butterfield. "You can spend a lot more than 500 bucks on other things that don't give you as much gratification."

Maybe so, but taken in the aggregate, America's green thumb adds up to some serious cash. Here's how gardening stacks up next to some other figures in the $38 billion neighborhood.

--Susan Q. Stranahan

AMOUNT SPENT ANNUALLY ON GARDENING = FEDERAL AID TO EDUCATION = ANNUAL REVENUES OF AOL TIME WARNER = ANNUAL EXPENDITURES ON LOTTERY TICKETS = GROSS DOMESTIC PRODUCT OF MOROCCO