BELLEFONTE, Pa. (AP) In a barn outside this central Pennsylvania town, Mike Theuer hums while he removes from a pan of black goo from the oven.

The oven is part of Theuer's makeshift factory, where he has begun production of the perkiest little flower pots around.

A child psychologist turned coffeehouse owner turned industrial entrepreneur, Theuer developed a plant-and-flower starter pot containing coffee grounds that dissolves in the ground and feeds plants as it degrades.

His company, Grow Joe Inc., began when Theuer bought Cool Beans Coffee & Tea, a downtown coffee shop in Bellefonte. He hoped it would become a place teen-agers would hang out and study, with live music and poetry readings. But it was Theuer who got an education when he found out just how much coffee was thrown out.

''I was throwing away barrels, just barrels, of coffee grounds each week,'' Theuer said. ''This just wasn't right.''

Theuer had always heard that coffee grounds were good for plants he'd even used them himself on occasion but never knew why. So with mounds of grounds on his hands, he set out to learn what makes coffee so good.

Despite his lack of training Theuer's undergraduate degree was in English, his master's degree in psychology he began poring through gardening and horticulture resources, both those meant for the general public and technical journals.

Theuer learned that any complete fertilizer needs nitrogen, phosphates and potassium; that other nutrients can help, but only in very small quantities; that the best fertilizers promote the growth of microorganisms in the soil. He also found plenty of anecdotal evidence that coffee was beneficial, but no hard proof why.

''There's something that's unique in coffee grounds that's not found in any other material we know,'' Theuer said. ''We know it has some nitrogen, and we know some microorganisms that benefit the plant directly are stimulated by coffee grounds. We just don't know why.''

With what he knew, Theuer began mixing his leftover coffee grounds with other organic leftovers dried blood for nitrogen, bone meal for phosphorus, potash for potassium. He added limestone to help neutralize the acid from the coffee grounds.

The result was Grow Joe fertilizer, the first marketable byproduct from Theuer's coffee bar. Theuer sent samples to Jay Holcomb, a professor of floriculture at nearby Penn State University who said Grow Joe was ''very comparable'' to most commercial fertilizers.

He also sent samples to gardening magazines and the general media, catching the attention of a Folgers freeze-drying plant in New Orleans. Folgers had plenty of coffee grounds to get rid of 20 tons, in fact and for the cost of shipping Theuer now had enough raw materials to begin experimenting.

While thinking of products he could make with his fertilizer, Theuer came upon peat pots, starter pots made from peat moss that dissolve when planted in the ground. If he could develop a similar pot, he'd have a definite advantage in the marketplace.

''There's not much nutrient value in peat moss,'' Holcomb said, ''whereas the Grow Joe pots do have some nutrient value and the plants can, essentially, get some of their nutrients from the pot as they grow.''

Theuer began studying plastics and polymers, looking for ways to mold his fertilizer into a solid form, eventually receiving pellets made from a plant-based plastic.

''I was melting pellets in the oven in my kitchen, mixing in fertilizer, trying to find the right mixture,'' Theuer said. ''My wife was having a fit.''

After soliciting financial support, Grow Joe became Grow Joe Inc. Theuer built a makeshift factory in an investor's barn, using an old oven, a livestock feeder and a collection of presses and molds he largely designed himself.

''I think it's amazing that he's actually made stuff, given the resources that he has,'' said Greg Dylan, a research engineer at Penn State who was asked to advise Grow Joe on production after Theuer had already built his little production line. ''For a guy who doesn't have any technical training, the way he's managed to put together this miniature production unit is amazing.''

Theuer's first prototype pots went to gardening magazines and garden-supply stores, including Smith & Hawken. The San Francisco-based company put in an order for 6,000 pots.

''We're very concerned, we've always been very concerned, about products that are good for the environment,'' Smith & Hawken chief executive officer Barry Gilbert said. ''Here was a unique product that was both good for the plant and good for the environment. It's made of recycled materials, and it's also nourishment for the plant what could be better?''

The order was too big for Theuer's makeshift factory, so he outsourced the Smith & Hawken order to a manufacturer in Russell, along Pennsylvania's Northern Tier. The first shipment arrived at Smith & Hawken in late March, and Gilbert said he didn't know yet how popular the pots were.

Still humming in his workshop, Theuer said he'd like to see his pots make it big, but he's fine either way.

''After all, I wasn't in this for the money,'' he said. ''I'm just an accidental businessman.''

On the Net:

GrowJoe, http://www.growjoe.com

Penn State University, http://www.psu.edu

Smith & Hawken, http://www.smithandhawken.com