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Growing Shiitake Mushrooms

First, the basics. Shiitakes are lignicolous, which means that they feed on lignin, a complex polymer that gives trees their structural strength - the heartwood of a tree is largely lignin. When a freshly cut log is inoculated with shiitake spores, the fungus takes over and colonizes the log. (All mushrooms are the fruiting bodies of fungi, and appear when conditions are right.) Normally, once a fungus has colonized a log, it keeps out all other fungi.

Here what to do: First you'll need some 3-6 inch diameter logs cut into 3-4 foot sections. They need to be cut for the project, not from trees that fell down, as other spores may have already inoculated dead wood. I use oak or poplar logs. Oak logs produce mushrooms intermittently each summer for 5-6 years before they rot and stop producing; poplar might last only 3-4 years, but start producing sooner than oak for me. Most hardwoods (beech, birch etc) are fine, but apparently sugar maple is not ideal. Don't use any conifers or fruitwoods, either. Call a firewood supplier if you have no suitable trees.

Then you'll need some commercially prepared spores to inoculate your logs. I buy mine from Paul Goland of Hardscrabble Enterprises (P.O. Box 1124, Franklin, W. Virgina 26807 or 304-358-2921). Shiitake spores come either as inoculated hardwood plugs or as thimble spawn; I've used both. Hardwood plugs are a tad easier to insert, but the thimble spawn have produced better for me and fruited earlier. They're not expensive: enough thimble spawn for 10 logs, a good quantity to start with, costs $13, plus $6 shipping. Quality and freshness of spawn is very important, and Goland has the best I've tried.

The innoculation process is easy. You drill rows of holes in the logs and tap spore plugs in with a hammer. Hardwood plugs have to be sealed off with hot food-grade wax to prevent drying out during the time it takes to get the log fully colonized. An old electric frying pan set at 300 degrees is perfect. A small paintbrush will serve to apply it.

Thimble spawn is made from sawdust and formed into thimble-shaped plugs, each with a little styrofoam cap and embedded in a sheet of molded plastic. That cap serves to seal off the sawdust plug once installed, so no hot wax is needed - a big plus for me. If a cap fell off, I used a screwdriver to push the spawn in more, then fit the styrofoam into the hole.

A four-inch diameter log needs three or four rows of holes drilled in it, with the holes spaced 6-8 inches apart in the rows.

The best place to store your logs is in deep shade; I lean them up against a hemlock tree. Some growers stack them in log-cabin type arrangements, though I like to stand them up, leaning against a tree trunk. That way I can rotate them to pick mushrooms -or to look for them. I place the butt of each log on a scrap of lumber or a flat stone.

Then what? Go have a cup of tea and feel smug. Your shiitake logs will just do their thing - when they feel like it, of course. Unlike your garden vegetables, shiitakes need no weeding, though in dry summers they might need a little watering. You shouldn't let them dry out.

You can't predict when shiitake logs will start blooming - in as little as four months of warm weather according to Goland, or as long as 15 months. In the winter they don't do anything.

You can force a "bloom" of mushrooms if you plan a week to 10 days in advance. Company coming? On a hot day, say 85 degrees or so, plunge logs into cold water (65 degrees or cooler) and let them soak. I have a long plastic wheelbarrow I fill with water; I float a few logs and let the logs soak for 12-36 hours, then retrieve them. Within a week I usually see some mushrooms popping out of the log.

Harwood logs inoculated with commercially prepared spawn will almost never produce anything but shiitakes; most poisonous mushrooms grow in soil and look nothing like shiitakes. Still, when your mushroom logs first start to produce, you may want to buy one mushroom at the grocery store to compare their looks - to put your mind at ease.

The last time I looked, organic shiitakes cost more than $10/lb, so it doesn't take long to recoup your initial investment in time and materials. I inoculate a few logs every other year in order to keep the shiitakes coming, year after year. That's the wonderful part of this gardening - there's very little you need to do once you've got them started. It's still a long way to gardening season, alas, but starting a few mushrooms now gives me a sense that I've already started the garden.

Henry Homeyer is the VT/NH associate editor of People, Places and Plants magazine. His website is www.gardening-guy.com.