Pioppini mushrooms, also known as shimeji or beech mushrooms, grow wild in forests in Japan and other parts of Asia. They are a delicacy enjoyed around the world, and their rich earthy flavor pairs well with red meats and long-simmering dishes. Pioppinis have been cultivated for several years commercially, and a few online vendors sell pioppini spores to home gardeners. It is not difficult to prepare them for growth but they require a relatively narrow range of temperatures and must be monitored continually.
Tear off the outer layer on one side of each piece of corrugated cardboard to expose the ribbing inside. Thoroughly mist the cardboard with a plant mister until it is saturated but not dripping.
Spread the sawdust impregnated with the pioppini spore over the ribbed side of each piece of cardboard, following the instructions that came with the spore to make sure that the density of coverage is correct. Lightly press the sawdust into the cardboard with the palm of your hand to make sure it adheres to the wet surface.
Roll the cardboard from the long side like a jelly roll. The roll should be tight enough to ensure that there are no open pockets between layers but not so tight that it impedes the growth of the spore. Tie the ends closed with twine or tuck the ends underneath the roll to close.
Find a suitable growing location for the pioppini. This may be indoors or outdoors depending on where you live in the country and the weather conditions. Pioppini mushrooms require a consistent growing temperature of between 60 and 65 degrees Fahrenheit throughout their long 100-day growing season. If the outdoor temperature remains constant, lay the cardboard logs outside in a shaded location. A cool basement is a practical alternative in most areas of the country. Leave a thermometer beside the logs to monitor the air temperature. Keep the logs misted and damp at all times.
Check for mushroom growth after 3 months. Bumps will begin to emerge from the cardboard and the mushrooms will begin to protrude in clusters, attached at the bottom like bananas. Continue to mist while the mushrooms are growing. Harvest the mushrooms when the largest ones in the cluster reach 3 or 4 inches long. Cut the entire bunch where the stems emerge from the cardboard. Pioppini mushrooms produce only a single crop so the cardboard can be composted after the harvest is complete.