Dean Fosdick/associated press Crates of fresh portabella mushrooms await packaging before being shipped from Phillips Mushroom Farms at Kennett Square, Pa. Portabellas are often called the "filet mignon" of mushrooms. They're favored by many vegetarians as a meat substitute.
KENNETT SQUARE, Pa. - Folks into fungi in and around this Brandywine Valley community - and there are many - like to say that mushroom growing isn't such a dark science. All you need is a healthy horse and shade.
Plenty of shade.
Seed the spawn in manure-rich compost inside a windowless building and, if the humidity, temperature and ventilation are right, you'll be able to pick a half-dozen crops or "flushes" of high-quality mushrooms at the end of a 12- to 16-week growing cycle.
Simplified though it may be, that formula has a lot of local pioneering going for it. Kennett Square has upwards of 85 farms listed in the Chester County Yellow Pages. Pennsylvania produces nearly 50 percent of the nation's mushroom crop, with the bulk of that picked by hand at the scores of growing sheds concentrated here.
There are no compelling climatological or horticultural reasons to explain the region's extraordinary number of mushroom producers.
"Most likely good access to markets," said Jim Angelucci, general manager of Phillips Mushroom Farms, which claims to be the largest grower of specialty mushrooms in the United States.
Buyers of the fresh fungi are just a short haul away in Philadelphia, Baltimore and other cities. Mushrooms have been cultivated here since the 1890s, initially by a few carnation growers who wanted to utilize wasted space in their greenhouses and generate new income from an alternative, off-season crop.
It didn't hurt that area racetracks were willing to give away sizable accumulations of nutrient-rich horse manure.
"They actually paid you to take it off the place," Angelucci said. "Now a truckload costs you anywhere from $1,000 to $1,500."
Essential stuff, manure, because the substrate, or growing medium, is one of the most important components in mushroom cultivation, Angelucci said.
"Ground up corncobs, cottonseed hulls and shredded hardwood bark are good sources of carbon; poultry manure, horse manure and ammonium nitrate provide the necessary nitrogen. Add air and water and a little gypsum to balance the pH (acidity)."
It isn't uncommon for groups of commercial growers to establish compost cooperatives where huge stacks of decomposing material are watered, aged, blended and pasteurized, the latter to kill any lingering insects, before being delivered to climate-controlled mushroom houses.
There, the compost is spread over rows of stacked wooden trays, sterilized and sprinkled with spawn. The temperature is dropped, the humidity raised and the mycelium - small, root-like filaments - begin threading their way through the substrate. At that point, a thin layer of enriched soil, the casing, is added to the top of the compost. Pickers will start gathering fully fruited mushrooms from the beds in a matter of weeks.
"Mushrooms are one of the most difficult commodities to grow," the American Mushroom Institute says. "Intensive labor is required to produce a consistent, high quality crop. Also, mushroom farms today are highly technical operations, complete with extensive computerized systems to monitor each point in production."
William Phillips, who founded Phillips Mushroom Farms in 1926, is one of several growers credited with bringing ice and eventually air conditioning to summertime mushroom production. That made it into a viable year-round crop.
Donald Phillips and his brother, Marshall, took over management in the mid-1960s, eventually steering the farms away from the white varietals and into exotics: portabella (the large "filet mignon" of specialty mushrooms), shiitake (a fibrous mushroom commonly grown on dead broadleaf logs), enoki (tender white mushroom that thrives in cool temperatures), oyster (matures in an array of colors and sizes with a mild taste), maitake ("hen-of-the-woods" with rich flavors) and pom poms (delicate, sweet taste often compared to lobster or veal), among others.
An estimated 70,000 mushroom species have been identified worldwide, though only about 10,000 grow in North America. At least 70 to 80 of the wild varieties are toxic, and some are downright lethal, including the aptly named "destroying angel" and "death cap."
Among edible fungi, the most highly sought include truffles, morels, chanterelles, black trumpets and porcini.
Perhaps the easiest mushrooms for novices to grow are oysters and shiitake. Kits are available that duplicate commercial cultivation, and make mushroom farming something you can do quickly and conveniently from home. Most are sent with spawn already injected into a growing medium. Just mist the maturing plant each day and expose it to temperatures ranging from the mid-50s to mid-60s.
Aside from their pleasing flavors, mushrooms have high nutritional value. They're rich in copper and potassium, niacin, the antioxidant selenium and B-vitamins.
"White button mushrooms contain more protein than kidney beans," the U.S. Department of Agriculture says. "Two-thirds of a cup of sliced, grilled portabella mushrooms contains the same amount of potassium as a medium-sized banana."
Vegetarians often choose mushrooms as meat substitutes, the sandwich-sized portabella cap in particular. Also spelled "portobello" and "portobella," it provides flavors difficult to achieve with vegetables alone, writes Jack Czarnecki, in "Portobello Cookbook" (Artisan).
"... For the person looking for gustatory satisfaction without the fat and the calories, portobellos could be the answer," Czarnecki says.
On the Net
American Mushroom Institute: http://www.americanmushroom.org