The little town of Kennett Square, Pennsylvania, hardly seems like an agricultural hotspot. In fact, the rolling hills around Kennett Square are not covered by farm fields at all. Tucked away in the southeastern corner of the state, near Maryland and Delaware, it is primarily known for its quaint architecture and as the hometown of Herb Pennock, an early baseball star who was inducted into the National Baseball Hall of Fame in 1948. Even so, farming is an important part of the local economy, but here in Kennett Square, all of the farming is done indoors. This town of 5,300 calls itself the Mushroom Capital of the World, producing more than half of all the domesticated fungi grown in this country.
The rise of Kennett Square as the mushroom capital was hardly inevitable. Cultivated mushrooms, after all, require no special soil or climate that would dictate one growing area over another. Rather, the town’s ascension was due to a timely combination of happenstance and economic logic. The mushroom industry here dates to the turn of the twentieth century, when Kennett Square was already well established as a center for growing hothouse flowers for the floral trade (particularly carnations).
Kennett Square’s mushroom heritage got its start when a Quaker farmer named William Swayne figured he could stack a second crop in his greenhouse and grow mushrooms in the damp, dark area underneath his flower benches. This would have been nothing more than a happy bit of trivia if it hadn’t been for the town’s central location, convenient to the major markets of Philadelphia, Pittsburgh, Buffalo, Baltimore, Washington, D.C., and New York. These cities provided the kind of educated, ethnically diverse consumers who would eat mushrooms, which at that time were not a popular item. Just as important, these cities were rich in the stuff that was necessary for mushrooms to grow—mainly horse manure, hay and straw. Trains bound for the big cities would roll out of Kennett Square loaded with mushrooms and return loaded with the collected detritus of those urban areas. By 1924, 85 percent of the mushrooms in the United States were grown in Pennsylvania, and by far most of them were grown in the Kennett Square area. Much has changed in the mushroom industry since then—notably, it is much less dependent on horses—but Kennett Square is still the center of mushroom propagation.
Dozens of varieties of mushrooms are commercially cultivated around the world, but more than 90 percent of those grown in the United States belong to one species— Agaricus bisporus. This familiar white mushroom was domesticated in Paris during the 1800s (in old texts you may find it referred to as champignon de Paris).
A brown variant of the same mushroom is sold as the crimini, and overgrown crimini are sold as portabellos. Fresh shiitakes (Lentinus edodes) are probably the next most common domesticated mushrooms, but there are also plenty of oyster mushrooms (Pleurotus) species around, as well as enoki (Flammulina velutipes). If you shop at Asian markets, you’ll find an overgrown oyster called the king eryngii (Pleurotus eryngii); the maitake, or hen-of-the-woods (Grifola frondosa); and the hon-shimeji (Hypsizygus tessulatus).
The challenge mushroom farmers face is converting wild mushrooms to domestic cultivation. This is more difficult than it may seem. Although white mushrooms will take root in beds of straw and manure, and oysters and shiitakes can be raised on dead tree trunks, other mushrooms, such as boletes (cèpes or porcini), chanterelles and truffles, live in symbiotic relationships with the root systems of living trees—a tricky situation to replicate artificially. Progress has even been made in cultivating fresh morels (Morchella esculenta), but there is still a way to go in formulating the ideal growing medium before these wild delicacies can become a supermarket staple.
Whatever the variety, mushrooms do not grow from seeds, but from spores. To grow white mushrooms, these spores are planted in big trays of specially formulated, sterilized compost made from the selected refuse of several different industries: cocoa bean hulls, cottonseeds, straw and ground corncobs. These beds are stacked several deep in long, windowless cinder block buildings. Two to three weeks after the spores are planted, the root systems of the mushrooms take hold. Called mycelia, the roots resemble lacy white threads. The mycelia are covered with peat moss, and within a couple of more weeks, the first mushroom caps begin to emerge. These are allowed to mature for another week or so before harvesting. The mushroom harvest takes place over about a week, and then the “mushroom house” is stripped down and sterilized before a new cycle begins. All told, it takes between a month and a month and a half to grow a mushroom crop from beginning to end.
The size of a mushroom is not dictated by its age. Mushrooms of the same maturity can range from a tiny button to a larger cap. The best indicator of age is the degree to which the mushroom has flattened out, exposing the gills underneath.
The portabello mushroom is simply a brown crimini mushroom that is allowed to mature for another week. This results not only in the mushroom’s being bigger (portabellos can weigh as much as a quarter pound each, whereas it takes 25 to 30 crimini to make a pound) but also in completely exposed gills and a softer texture. For years these mushrooms were regarded as expensive mistakes—a sign that a mushroom house had been poorly maintained—and were discarded as not worth selling.
Then, in the early 1990s, a marketer got the bright idea of selling them to restaurants as “domestic wild” mushrooms. The name “portabello” was invented because it sounded Italian (it is a completely made-up word, and there is no agreement on spelling; you’ll see them labeled “portobello,” “portabella,” “portobella” and “portabello”). The idea took off. So popular have portabellos become that crimini are now sometimes marketed as Baby Bellos.
When you taste portabellos and crimini side by side, it’s hard to tell whether there is much of a difference in flavor. But there is a big difference in texture: crimini are much firmer, while portabellos are meatier. Crimini are better for using raw, as in salads, while portabellos are better for grilling. There is one other difference: portabellos have fully mature gills, which stain everything they touch a rather dismal gray. The gills are easily cut away, though.
Mushrooms have become popular well beyond anyone in Kennett Square’s wildest dreams. Since 1971 American per capita consumption has increased by more than eightfold. Americans now consume on average 2.6 pounds of fresh mushrooms every year. That is enough to make mushroom growing a more than $900-million-a-year business. Mushrooms are the fourth-leading vegetable in terms of value to farmers, behind only potatoes, tomatoes and lettuce. White buttons make up the vast majority of sales (better than 85 percent), but sales of brown mushrooms—both crimini and portabellos—are growing fast, as consumption of brown mushrooms has nearly doubled in the past decade.
WHERE THEY’RE GROWN: More than half of the mushrooms grown in the United States come from Pennsylvania. The next leading producer is California, with about 14 percent.
HOW TO CHOOSE: Mushrooms are predominantly water—between 80 and 90 percent—and the “skin” that covers their exterior is extremely thin. As a result, mushrooms dry out very quickly. Choose mushrooms that are smooth, glossy and wrinkle-free. Also avoid any that have obvious bruising, as damaged flesh breaks down very quickly.
HOW TO STORE: Store mushrooms in a paper bag or some other moisture-absorbing container in the refrigerator. Any moisture that collects on the mushrooms will quickly cause spoilage.
HOW TO PREPARE: For most mushrooms, you need to do little more than wipe them clean and cut away the hardened base of the stem. Contrary to popular belief, you can rinse mushrooms with water without causing any damage. (They are mostly made up of water to begin with.) But to avoid spoilage, do this just before you cook them, then wipe them dry so they’ll brown during cooking. Like apples and potatoes, mushrooms are very prone to enzymatic browning. Cut them up at the very last minute. If you must cut them up in advance, toss them with a little lemon juice to delay browning.
ONE SIMPLE DISH: When cooking mushrooms, here’s a good trick to get the best flavor: start the mushrooms in a hot pan and add the seasonings only after they’ve cooked a bit. When the mushrooms hit the hot butter, they’ll start to give off moisture. If you add the seasonings at this point, their flavor will carry back to the mushrooms as the liquid concentrates and is reabsorbed. Using a hot pan allows the mushrooms to brown a bit before they start to become limp. Mushrooms prepared this way are terrific as a side dish, served by themselves. A final gloss of butter and a couple of drops of sherry vinegar will round out the flavor nicely. Vary the herbs—maybe some rosemary (just a hint) or tarragon (as much as you want). You can use shallots or garlic. And sometimes it’s nice to toss in some chopped toasted hazelnuts for a bit of crunch.