Thomas Szaky shocked his parents a few years ago when he decided to drop out of Princeton University to start a business making plant food. To their dismay, he explained that the product came from worm poop.

But today, the 23-year-old Canadian is having the last laugh. His fledgling firm has landed a Wal-Mart Canada Corp. account, one of the most prized in retailing.

His product, which is packaged in recycled pop bottles, is also being tested at 10 Loblaw Cos. Ltd. stores and will launch in Zellers Inc. in the summer. And it is carried at some U.S. chains, such as Whole Foods, Shop Rite and Wegmans.

How did Mr. Szaky nab the business at mighty Wal-Mart? "Sixty phone calls and one of them works," he said in an interview yesterday. "It's sheer persistence."

He started his company, TerraCycle Inc., just two years ago after Mr. Szaky, as a first-year economics student at Princeton, got the idea of selling worm casings on a visit to a friend in Montreal who kept a worm box in his kitchen to make fertilizer for plant food. The plants were growing beautifully.

Always on the lookout for new business ideas, Mr. Szaky returned to Princeton and, with a friend in their spare time, wrote up a business plan for the organic plant food.

"No one was really doing it on a big scale," he said. "Everyone was doing it in their kitchen . . . I thought: 'There's got to be a neat business model there.' "

Based in Trenton, N.J., the fertilizer firm expects to generate $3-million (U.S.) of sales this year and as much as five times that amount in 2006, he said. It projects operating in the black within six months.

TerraCycle Plant Food is now being shipped to all 256 Wal-Mart stores across the country, and will get prominent shelf space, said Wal-Mart spokesman Kevin Groh. "It's not something we're tucking away in a corner of the store."

The chain, among the largest in the country, is responding to a burgeoning customer demand for organic gardening products, Mr. Groh said. It will continue to sell traditional plant foods and weed killers.

He said an array of jurisdictions across Canada are either looking into, or have already legislated bans or restrictions on the use of pesticides for lawn care. "It's obviously been on the radar screen of municipalities and various jurisdictions."

Last year, amid controversy, the City of Toronto enacted a bylaw to wean homeowners off using chemical products to kill lawn weeds and bugs. It joined about 70 other cities in Canada in tapping into bylaws to reduce, and in some cases ban, cosmetic use of legally sold pesticides.

Wal-Mart was also impressed that TerraCycle was working with schools to collect recycled bottles, and that the product was essentially made of waste, Mr. Groh said.

It costs about $4.50 (Canadian) for a 591-litre bottle and $8.97 for a one-litre bottle, slightly less than its chemical counterparts, Mr. Szaky said, adding that if the product sells well in Canada, Wal-Mart stores in the United States could stock it.

Zellers, too, is picking up on the popularity of organic and environmentally friendly items, said Hillary Stauth, a spokeswoman for Hudson's Bay Co., which owns the 298-outlet retailer. "It's this kind of fresh, innovative merchandise that resonates with consumers and brings them into our stores."

Mr. Szaky said his plant food has outperformed the leading chemical alternatives food "in many aspects of plant growth" in tests done at Rutgers University.

Never a staunch environmentalist, the former Toronto resident said he began working on his worm project during the summer after his first year at Princeton.

He and three friends raised a stunning $20,000 (U.S.) from friends, spending their time "shovelling rotting food waste" to feed to worms and make the product. The young men won a number of university business-plan contests, which helped finance the project.

TerraCycle organizes students across North America to collect pop bottles for the containers, paying 5 cents a bottle, while also cutting deals with bottling plants for a half-cent a bottle, he said.