Subtitles section Play video Print subtitles Farmers grow harvest and pack nearly 400 million mushrooms a year in this small pennsylvania town. Here they cultivate everything from white button and portobello to specialty mushrooms like shiitake and lion's mane mushrooms. Eat a strict diet of recycled mulch hay, wheat, straw, poultry litter and corn. Cob mushrooms are grown indoors so that we can control the environment. It all happens on vertical shelves. Workers use this machine to lay the compost down. Then comes a layer called casing, with peat, moss, limestone and water. After 16 days were ready to harvest mushrooms double in size every 24 hours, so pickers have to move quickly each armed with a knife, a cart and tons of boxes.