BALTIMORE (AP) _ The secret to Joe Mills' prodigious pumpkin patch is in the fertilizer. It's exotic, all natural _ and there's a ton of it.

That's how much elephant manure the museum photographer ordered this year from the National Zoo in Washington for use on his 1,300-square-foot garden in Virginia.

Zoos from Washington state to Washington, D.C., are fulfilling gardeners' dreams _ and making money _ by selling elephant, hippo and giraffe manure as fertilizer, turning a stinky problem into sweet-smelling success.

Gardeners praise the nutrient-rich manure for producing bumper crops. The Seattle zoo is already sold out for the season. And one company, ZooDoo of Memphis, Tenn., sold almost $500,000 worth of animal-shaped manure products such as ``Dung Bunnies'' and ``CrocADoos,'' thanks to a continuing supply from the nearby Memphis Zoo.

``The year I used it, I got a 408-pound pumpkin,'' said Mills, of Falls Church, Va., a Washington suburb. ``It drains well; it adds nutrients. It's great stuff. It even smells good.''

Well, not at first, as anyone who has been to an elephant house in July will attest. A full-grown elephant produces about 300 pounds of manure per day, said Rick Reichley, self-proclaimed ``ZooDoo'' expert at the National Zoo, which has four elephants.

Turning the waste into fertilizer is great, Reichley said, but not all zoos can do it because of the space needed for the compost pile and the manpower needed to keep it going.

``These animals are producing about 1,500 to 2,000 pounds of poop a day and they don't take any days off,'' said Reichley. ``We're almost to the point where we're going to give it away.''

Other zoos either burn the manure, pay to send it to landfills or use it on zoo flowerbeds.

``Ours is hauled to a mushroom farmer in Pennsylvania, who composts it. I think a blueberry farmer also gets a share,'' said Steve Linda, chief horticulturist for the Baltimore Zoo, which has a small composting plot it uses for zoo grounds. ``We use it around everything: roses, vegetable gardens.''

The ZooDoo program at the Woodlawn Park Zoo in Seattle is so popular that the recycling coordinator uses a lottery to determine who gets to put a load in their pickup truck. Although the zoo is sold out for the season, there are 200 people on the waiting list, just in case.

``Sometimes people show up with plates of cookies and cannolis, but we have a stringent code of ethics,'' said Tom Gannon, who has a master's degree in environmental management. He said the zoo makes about $18,000 from its annual fertilizer sale.

Woodlawn started the program about a decade ago, when the zoo was trying to save money on skyrocketing landfill fees. Now Gannon composts almost 100 percent of the manure from the zoo's plant-eating animals and sells it for around $1 for 25 pounds.

Zoos only use the manure from herbivores, such as elephants, giraffes and hippos. There is some concern about toxins in carnivore manure.

Lewis Smith, a scientist for the Agriculture Research Service in Greenbelt, Md., is not all that impressed by the exotic-animal waste. ``It's probably not a whole lot different than cow manure by the time it's composted,'' he says.