They're not plants. They're not animals. Mushrooms, that perennial dinnertime favorite, exist in their own biological world, thriving in conditions that would doom most crops.

“This is an entirely different kingdom from vegetables,” says Jesse Tobin of Primordia Mushroom Farm in Berks County. “We don’t have the same rules.”

That difference shapes everything about modern mushroom cultivation, from the sterile laboratories where the process begins to the carefully controlled environments where mushrooms fruit.

While vegetables are plants that photosynthesize and grow in soil, mushrooms are fungi – organisms more closely related to animals than plants. They don’t need sunlight. They don’t have roots, leaves, or chlorophyll. Instead, they digest organic matter externally, using enzymes to break down their food before absorbing its nutrients.

Their basic biology means mushroom farming looks nothing like traditional agriculture. There are no fields, no tractors plowing rows, no concerns about weeds competing for sunlight and nutrients. Instead, growers obsess over sterility, humidity, and precise temperature control.

“When people think of veggie farms, they probably think of having rows of soil,” says Matthew Sicher, who co-owns Primordia with Tobin. “Here, we’re creating a sterile environment for fungi and bacteria to grow. The emphasis is on sterility. If our growth process goes wrong, we’re left with really expensive compost."

The mushroom lifecycle begins microscopically. Growers start with cultures in petri dishes — specific genetic specimens chosen for their growing characteristics and flavor profiles. “All varieties are clones, based on the specimens,” Sicher explains. This cloning process ensures consistency and predictability.

From the petri dish, the culture moves to “spawn” — grain or sawdust inoculated with mushroom mycelium, the threadlike vegetative part of the fungus. This spawn is then mixed with substrate in grow bags. At Primordia, that substrate is sterilized hardwood sawdust from local oak and poplar, supplemented with nutrients.

The timeline varies. Oyster mushrooms might fruit in four weeks from inoculation. Shiitake takes 12 to 14 weeks. Each variety demands slightly different conditions during colonization, when mycelium spreads through the substrate, and fruiting, when the actual mushrooms emerge.

The diversity of mushroom varieties surprises most consumers familiar only with the white buttons, cremini, and portobello they find at most grocery stores. (These three are actually the same species – Agaricus bisporus – harvested at different stages of maturity.)

Specialty growers like Primordia cultivate a much broader palette. Their 14 varieties include gray oyster, golden oyster, shiitake, maitake, lion’s mane, trumpet, pioppino, pink oyster, and reishi. Each brings distinct flavors and textures. Lighter-flavored mushrooms like golden oyster, trumpet, and lion’s mane pair well with poultry, fish, pasta, and white wine. Stronger varieties such as shiitake, maitake, and pioppino stand up to red meat and robust wines. Lion’s mane, with its sea- food-like texture, works brilliantly in vegetarian crab cakes. Reishi, prized for medicinal rather than culinary properties, gets brewed into tea or added to bone broth.

“They’re just so diverse, so much more so than people realize,” Sicher notes.

Unlike the bigger farms in Kennett Square, smaller-scale growers like Primordia focus on gourmet and wild varieties that command higher prices but require more hands-on cultivation. Instead of industrial-scale facilities, they operate barn-sized growing rooms on small family farms with mushrooms that are harder to cultivate and remain unfamiliar to most consumers.

“There has been a lot of customer education,” Sicher says. “A good seller for us has been the one-pound mixed bag, which includes a small amount of each mushroom. I often tell people, ‘Don’t be intimidated about cooking them. You don’t have to do anything fancy. Just marinate with onion and butter and garlic, and some salt to taste. Then experiment all you want.’”