Every three years or so, we tromp through our woods and find a small oak tree to harvest for growing shiitake mushrooms. A true high-value crop, shiitake mushrooms (Lentinula edodes) have been cultivated in China for thousands of years. Their woodsy flavor amps up the umami flavor factor in foods from brothy soups to white pizza, and recent research validates that eating shiitakes regularly enhances the immune system. For vegans, shiitakes provide a rare dietary source of Vitamin D.
Best Shiitake Logs
Getting started growing shiitake mushrooms is a project for late fall to late winter, when trees are dormant, because the sugars and other nutrients that feed shiitake fungi are most abundant in live, dormant wood. I look for a straight young oak 4-5 inches (10-12 cm) in diameter, that’s being crowded by larger trees. You can use other hardwoods for growing shiitake mushrooms, but oak has nutritious wood that rots slowly, with bark that persists a long time, keeping wood-rotting fungi other than shiitakes from taking over the logs. I like logs about 3 feet (1m) long. Shorter logs dry out too fast, and longer logs are too heavy to carry when they are soaking wet.
If you live in a city, call a local tree service to locate the shiitake logs of your dreams. One of my most successful crops ever was grown on wood from a big red oak that had fallen in a storm.
Shiitake Mushroom Plug Spawn
Growing shiitake mushrooms on logs is a fascinating gardening adventure because you are growing fungi rather than plants. Once you have logs, you need a starter culture to get the fungi going, which is called spawn. I like using plug spawn, which are pieces of hardwood dowel that have been impregnated with the shiitake fungus. Numerous mail order suppliers sell plug spawn. A packet of 100 plugs will inoculate 5 to 6 logs, which is a good-size crop for a home gardener.
Plug spawn is great because you get a tight “graft” when the dowels are pounded into 1-1/4-inch (32mm) deep holes drilled into the logs about 6 inches (15cm) apart. I use a regular drill with 3/8 inch (9mm) drill bit, which I mark with paint at the correct drilling depth.
Next, use a hammer to tap the plug spawn into the holes. The finishing touch is a coat of food-grade wax (such as cheese wax), which is dabbed over the filled holes to seal in moisture and exclude invading fungi. I melt wax in a metal food can set in a pan of hot water, and apply it to inoculated logs with a dauber made from cloth scraps attached to a stick with tight rubber bands.
Growing Shiitake Mushrooms
That’s it for the planting part. The shiitake logs are set to rest in a shady spot until white mycelium shows at the ends, which usually takes 8 to 14 months. Watering the logs during dry spells helps to keep the mycelium running. Shiitake logs will fruit naturally after a soaking rain when they are ready, but it’s better to induce fruiting by soaking two or three logs in cold water for 24 hours, and then giving each soaked log a solid knock with a hammer, which seems to excite the fungi. Rounded buttons, or pins, appear within days, and quickly mature into brown-capped shiitakes.
Shiitakes fruit best in spring and fall, with logs resting between flushes for three months or more. Individual logs will produce in spurts for three to five years, though production wanes as the fungi run out of food.
Harvest perfect mushrooms promptly, before they are discovered by snails and little beetles, and use a dry paintbrush to remove debris. Shiitakes will keep in the refrigerator for several days, or you can dry them. I like to cook shiitakes in big batches with a little olive oil and salt, and then add them to soups, risottos or pasta dishes. As with other mushrooms, shiitakes should be cooked for at least 12 minutes to enhance their nutritional value.