This weekend I will be attending the 32nd annual mushroom festival in Kennett Square Pennsylvania. In wake of these festivities, I thought it would be appropriate to feature a mushroom that is most cultivated in the States, and responsible for Kennett Square’s claim to fame as the mushroom capital of the world. Agaricus bisporus, when grown to a larger size are called portobellos in the supermarket, while smaller harvested individuals go by the name of creminis. In 1926, a white mutant variety of the same species appeared, and rapidly spread in popularity. Today, white button mushrooms, portobellos and creminis are grown and sold by the billions. We have Agaricus bisporus and Kennett Square to thank for these delectable fungal morsels.
Its scientific name, A. bisporus actually refers to microscopic features on the gill surfaces. Most gill forming mushrooms produce four spores on each basidia, but as you might have guessed, Agaricus bisporus produce but two. With these spores, media to grow in and the proper environmental conditions, these robust fruiting bodies are harvested and sold on a massive scale. More than 20 years ago, it was reported that 1.5 million tons of these species were produced!
Kennett Square Pennsylvania, the mushroom capital of the world.
Cultivation of mushrooms is actually a very recent phenomenon in human history. It wasn’t until 1893 when we discovered pasteurization techniques that humans started producing mushrooms on a commercial scale. Harvesting environmental mycelia and transplanting to suitable substrate carried other forest floor or grassland species that would compete with the selected fungus. Cultures not completely pure don’t readily fruit, so before spores are inoculated, the substrate must be pasteurized. Void of any other species, the selected species can readily colonize the substrate and fruit unperturbed.
Now, you might be wondering, why Kennett Square? This smaller nook of Pennsylvania doesn’t necessarily have the best growing conditions. Besides, almost all mushroom cultivation in the U.S. takes place in environmentally controlled facilities. A couple of factors play into Kennett Square being the mushroom capital of the world. For one, when techniques came about that made mushroom farming possible, Kennett Square had access to an enormous resource pool for fungal substrate. To this day, horse manure is used for cultivation, and with Kennett Square being so close to one of the largest American cities at the time, they literally had mountains of Philadelphian manure to work with. Another factor that contributed to widespread mushroom cultivation was man power. The original Quakers who grew the first batches of Agaricus bisporus were a hard-working bunch, most willing to get their hands dirty.
White phenotype of Agaricus bisporus.
Today, right outside Kennett Square lies a massive, 20-acre compost pile of hay, horse manure and since this is Pennsylvania, cocoa shells from the Hershey chocolate factory frequent the mix. People here respect the areas heritage, and carry those same hard-working traits the original mushroom farmers had. It really is crazy that 50% of Americas mushrooms are grown in this quaint corner of Pennsylvania. I am excited to see these large mushroom operations with my own eyes, but can seem to stop thinking about what these original operations looked like more than one hundred years ago.