How to Grow Your Own Shiitake Mushrooms

Mushrooms, the fruiting part of underground fungi, may be the strangest item we commonly find on our dinner plates, as they are neither plant nor animal. The largest living thing on Earth is a fungus nearly 4 miles long, and the underground threads of mycelium may act as a sort of internet between plants.

Delicious types like the shiitake have been foraged from the woods for millennia, and only more recently did they become the second most cultivated mushroom. Now it’s possible to buy a kit for growing mushrooms at home—a good place to start—but if you have a shady place at home and a couple of logs, you can raise your own delicious shiitake harvest.

How to Plant Shiitake Mushrooms

Planting mushrooms is quite different from planting vegetables. Commercial shiitakes may be grown indoors "planted" in plastic tubes stuffed with straw or sawdust, but this requires ventilation, temperature, and humidity controls. Creating a growing room is no small undertaking. Small growers tend to use the outdoor method of inoculating logs with "plugs" or a sawdust inoculant mix.

Choose a Location

Your outdoor location should be almost completely shaded, protected from the wind, and fairly humid. You will need a workspace to make holes in the logs using a power drill, a space to inoculate the logs, and a place to let them rest and bloom. You will need access to water, such as a hose or sprinkler, for maintenance and a tub for soaking logs when needed. And, of course, there must be some way to get the logs and gear to your site, as well as a way to take your harvest home.

Choose Your Logs

Whether you buy pre-cut wood, befriend a local arborist, or cut fresh logs yourself, similar criteria apply; the wood should be recently cut, clean, have the bark intact, and come from a hardwood tree such as oak, maple, beech, hickory, or black walnut. Do not use evergreens, softwoods, or fruit trees. Try cutting the wood about 3-6 inches across and 3-4 feet long, optimally in late winter or early spring. Store them off the ground to avoid decay and pests and in the shade to keep them from drying out. The logs must be fresh enough to hold the nutrition and moisture needed for the shiitake spawn to thrive.

Order Your "Plugs"

Loose shiitake inoculant is made up of sawdust and the stringy, fungal threads called "hyphae". More commonly, shiitake are started from “plugs” or “dowels”, short pegs of wood already fully colonized. The loose inoculant mix is cheaper and may colonize the wood more quickly, but the plugs are easier to handle. If they arrive before your logs are ready, plugs can be kept in the refrigerator.

Inoculate the Log

The process should begin in early spring to allow the shiitake to spread throughout the wood before going dormant in cold weather. 

Using a drill bit the same size as your plug, make holes every three inches and an inch deep. Drill the next rows 2 inches apart, offsetting the holes to make a diamond pattern. The number of rows on a log is equal to its diameter, so a 5-inch log should have 5 rows. For sawdust inoculant, use a 7/16 inch drill bit to make holes 1.25 inch deep.

Fill each hole with a plug, tapping it in with a mallet until it is just a bit further in than flush with the surface. If using sawdust, it’s best to use an inoculating tool.

Wax

Using a spreader (wooden tongue depressor or a sponge paintbrush, for example), cover each hole with a melted, food-friendly wax like paraffin, beeswax, or cheese-wax, sealing and protecting the inoculant. The wax should make a good seal but not protrude. Double check to make sure that it hasn't formed pinholes or cracks after drying, as these can let in pests or competing spores.

Shiitake Mushroom Care

Logs should be kept in a shady place and stacked log-cabin-style or leaned against a support to make an A-frame. Check frequently to make sure the logs are not drying out, and hose them down if they are. In winter, inoculated logs can be covered with breathable burlap or straw to insulate until warmth and moisture cue the fungus to fruit.

According to Dr. Perry, the process of spawning and colonizing the log will take 8 to 18 months. The shiitake should fruit in their own time, as the weather warms up in spring, but you can hurry things along by "shocking" them, soaking them in cold water for 12-24 hours, and then leaning them in the A-frame style or up against a building until small, white bumps appear in a few days. Shiitakes will be ready to harvest in about 7-10 days after shocking. In the meantime, protect them from wind, frost, and slugs.

Common Pests and Diseases

According to Danny Lee Rinker of the University of Guelph, fungus gnats are especially problematic for indoor mushrooms as their larva eat the mushroom from inside and can do a lot of damage to the mycelia, especially a few days after spawning. Sticky traps will help monitor and catch adult gnats. Outdoors, slugs can be a nuisance but can be "trapped" in wet newspaper and removed. Ants can be deterred with diatomaceous earth and furry nibblers like squirrels, chipmunks, or deer can be put off by a light fabric such as Agribon.

How to Harvest and Store Shiitake Mushrooms

Shiitakes should be harvested while the cap is still partially curled downward, as they will have a better texture than those that have already flattened out or curled up at the edges. With scissors or a sharp knife, cut above the log's or substrate’s surface in order to keep debris off the stem and out of the gills. Once harvested, Fungi Ally recommends mushrooms be cooled immediately and kept at 36 degrees F.

Mushrooms can be dried in a dehydrator—or in the oven at its lowest temperature—until they are dry but still leathery and flexible. To cook with dried shiitakes, simply soak them in warm water for 20 minutes before using.