Green Island, N.Y. ? Turns out that mushrooms — great in soups and salads — also make decent packaging material.

Mushrooms are a key ingredient in the pale, soft blocks produced by the thousands in an upstate New York plant that are used to cushion products ranging from Dell Inc. servers to furniture for Crate and Barrel.

More precisely, the packaging blocks are made with mycelium — the hidden “roots” of the mushroom that usually thread beneath dirt or wood. Two former mechanical engineering and design students, Eben Bayer and Gavin McIntyre, figured out how to grow those cottony filaments in a way that binds together seed husks or other agricultural byproducts into preset packaging shapes.

Their 5-year-old company, Ecovative Design, has a toe-hold in the increasingly lucrative market for eco-friendly alternatives to plastic foams — and their business is growing like shiitakes on a damp log. Bayer and McIntyre are already expanding their line for everything from footwear to car bumpers.

“We want to be the Dow or DuPont of this century,” Bayer said.

If the aspiration sounds grandiose, consider that six years ago Bayer and McIntyre were Rensselaer Polytechnic Institute students growing fungus under their beds for a class project. Today, the young entrepreneurs are more than doubling their production space and recently announced a deal with Sealed Air Corp., the packaging giant known for Bubble Wrap.

Not bad for a product that grows itself.

Workers at Ecovative inoculate mycelium into pasteurized bits of seed husks or plant stalks, then place the mix into clear plastic molds shaped like the desired packaging pieces, such as a cradle-shaped mold for a wine bottle. The mix is covered for about five days as millions of mycelium strands grow around and through the feedstock, acting as a kind of glue. The piece is heat dried to kill the fungus, insuring that mushrooms can’t sprout from it. Since the mycelium is cloned, the product does not include spores, which can trigger allergies. The packaging is edible, technically, though it does not appear appetizing and is not recommended as a snack.

“It’s low-tech biotech,” Bayer said.

Bayer noticed mycelium’s “stretchy” properties as a kid growing up on a Vermont farm. As students, he and McIntyre started with mushroom-based insulation, but the pair switched to packaging material because it seemed a better business bet. They experimented with common varieties like the oyster mushrooms before hitting on just the right (secret) mix.

The company moved several years ago to a 10,000-square-foot facility in Green Island that still has the feel of a startup: an old industrial asparagus blancher pasteurizes the feedstock, and the mycelium is applied with a machine that once put chocolate chips on cookies. McIntyre’s pet chinchilla, Audrey, rolls around the offices in a plastic pet ball.

Bayer said Ecovative, with 42 employees, has attracted more than $10 million in grants and equity investment, as well as some big-name clients. Dell director of procurement Oliver Campbell said his company has a pilot program using the Ecovative product instead of polyethylene foam for shipping a high-end server.

“To cushion $25,000 worth of servers with mushrooms, that’s kind of a radical thought,” Campbell said.

But Campbell said the technology fits Dell’s green initiative. It probably helped that Campbell was a mushroom guy who grew shiitake mushrooms for sale with his wife.