What Is a Chestnut Mushroom?

Also known as the pioppino or black poplar mushroom, the chestnut mushroom, or Agrocybe aegerita, is a fungus coveted in both culinary and herbalist circles. Starting out white, then slowly turning brown, this species grows in clumps on live trees, fallen logs or stumps, in mostly subtropical regions of the world. Wild mushroom hunters and gourmet mushroom growers give it high marks for taste, texture and ease of cultivation. Chinese biotechnologists also have discovered powerful metabolites in this mushroom with alleged antibacterial, antioxidant and anti-cancer properties.

Wild mushrooms with caps that are gilled on their undersides are members of the Agaricales order of the Agaricaceae class. Perhaps the most ubiquitous members of this order are the lightly gilled button mushrooms called Agaricus bisporus and the widely gilled meadow or field mushrooms known as Agaricus campestris. The chestnut mushroom, which some have tried to alternatively classify as Agrocybe cylindracea, is reputed to have a nuttier and slightly sweeter flavor than these others and can grow to a diameter of as much as 4 inches (about 10 cm).

The chestnut mushroom and many other Agrocybe plants may be prized for a savory flavor and meaty texture; however, they closely resemble others that are either poisonous, hallucinogenic or both. For instance, the Japanese Agrocybe farinacea contains the recreational hallucinogen psilocybin. An African variety in the order Agrocybe putaminum may produce hallucinogenic effects, too — just before it kills those who eat it.

Science is slowly catching up to folkloric knowledge of the chestnut mushroom as a potent homeopathic drug. Though more research appears to be needed in 2011, constituents of this fungus appear to have antiseptic, antifungal and antioxidant powers. Perhaps most striking is the chestnut mushroom's ability to kill cancerous cells, according to the 2009 book Biotechnology in China I: From Bioreaction to Bioseparation and Bioremediation, a joint venture of the Chinese Academy of Sciences, the Shanghai Jiao Tong University and the Dalian University of Technology.

Since many Agrocybe mushrooms are edible and others are toxic — even under cursory microscopic review — many mushroomers advise novice hunters to steer clear of wild Agrocybes. A safer alternative is to cultivate them on fallen logs, stumps or even in wood chips or sawdust. This often requires the purchase of a fungal culture, a growing medium like perlite or rice flour, and moderate temperatures ranging between 50 and 70°F (from 10 to 21°C). The process also will require a moist environment where fungus is most apt to form naturally.