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Fun with fungi – shiitake mushrooms

May 5, 2011

Down in the woods, under what might be a mildly radioactive rain, we are witnessing an explosion of Japanese shiitake mushrooms. The earthy edible fungus is a treasure for those of us (grown-ups) who want to slice and stir-fry it, and also for those of us (children) who want to venture into the forest with baskets and bowls to gather something special. For all of us, it seems a magical experience to find boisterous growth from what looked more dead than dormant.

I started growing shiitake mushrooms in the spring of 2009. I learned how to do it from Julie Winslow of Cape Coastal Products, who was kind enough to invite me over to help with the spring inoculation. The farm boasted row after row of carefully labelled logs resting under the protective shade of trees. Julie welcomed me into her steamy greenhouse filled with lamb’s quarters and logs and the scent of hot wax. I’m not sure how much “help” I was, but I asked a zillion questions, learned a lot about shiitake mushroom farming and, most importantly, got to try my hand at impregnating logs with mushroom spores.

Julie had a special high-speed electric drill with a custom 5/16ths-in-diameter bit that stopped at just the right depth (one-and-a-quarter-inch). “You could use a metal drill,” she offered after telling me about her Japanese drill made specifically for shiitake inoculation. I do have a high-speed metal drill, so I figured I was good to go. She was using loose sawdust spawn, which is just what it sounds like – loose, damp sawdust that has been seeded with shiitake mushroom spawn. We drilled holes in a diamond pattern, six-inches apart from log end to log end, and two- or three-inches apart around the girth of the log.  Then we got to the fun part.

Julie also had a special palm thrust inoculator, a tool that you can scoop up the spawn with and then hammer it home into the holes in the logs. The technique involved jamming the tool into the bag of spawn to fill the tool’s open end, then centering it over the hole and banging the top of the tool to punch it into the log. It took a little practice to avoid jamming too hard (packing too much in the tool) or jamming too soft (not enough spawn in the tool) and also making sure, after the punch, that the hole was filled but not over-filled.

Once all the holes were filled we began sealing them with melted wax. Julie had a hot plate set up in the greenhouse with a two-quart sauce pan filled to a depth of three-inches with hot wax. Dip a cotton dauber in the wax, paint the stuff over the holes, and – viola! – the logs are ready to rest for the summer. The seal prevents the spawn from drying out and prevents contamination. “Smaller-diameter logs may sprout some mushrooms this summer,” Julie said. “But your big bloom will come the following year.” Very big logs can continue to produce mushrooms for several years, while the spindly ones will burn out sooner. Logs need to be kept out of direct sunlight and it is important to avoid letting them dry out. If there is a drought, they should be hosed down periodically. They can be crib-stacked, but when they begin to fruit they should be upright to facilitate gathering (lean them up against something.)

After some time drilling, jamming, punching and painting, the short tether of momdom began to yank at me and I had to go, but I left armed with not only knowledge but also a bag of spawn Julie sold me – along with an inoculation tool, special stoppered bit, and book about shiitake farming from Field Forest Products on lend. I headed home excited to make use of the oak logs I had saved from a tree taken down a few months earlier. The tree in question, the heart of my shiitake experiment, was felled because it was on its last leg, but I hoped it had enough juice left in it to provide a growing environment for the shiitake mycelium.

Mycelium, you say? Well, yes, that’s how this whole thing works. The spores introduced to the log feed on the wood, growing throughout the log as the mycelium decomposes the various components (such as lignin) within. Once the thready strands of mycelium have consumed the needed nutrients for growth, they will try to reproduce by sending out fungus that can release its spores into the air. Mushrooms spotted popping up in the forest are also connected to a mass of mycelium underground. Paul Stamets, in Mycelium Running discusses a 2,400-acre mat of mycelium in eastern Oregon that was estimated to be 2,200 years old. A four-foot-long,  five-inch diameter log does not contain enough nutrients to support that kind of growth, but, needless to say, the bigger the better for long-term growth. The only limitation is ease of handling, so eight-inches was our maximum diameter.

A few days later, tools and spawn in hand, we set up a table in the garage, tapped a keg of homebrew and got to work. I knew we could use beeswax, and also paraffin for the sealing so I heated up a mix of the two. Our beeswax came from spent frames from our beehives, so it was not exactly clean, and as we ran out of wax and relied on used frames it became more of a murky melt. We also ran out of logs, which worked out well as I was able to cut some fresh, healthy oak as an insurance policy in case the wood from the near-death tree was inhospitable to fungal growth.

All the logs grew ‘shrooms, and some popped out that season. The following year I ordered sawdust spawn and borrowed another inoculator and bit from another shiitake grower in town (how many of us shiitake fanatics are there on Cape Cod? We might have to form a support group!) We pruned trees here and there and put together another batch of logs. Soon after we stacked the new logs, the first batch started blooming in earnest. We gathered them, sauteed them, added them to soups and gave them away, but as the season progressed I knew we couldn’t keep up with the fruiting.

I put the dehydrators to work. We have two five-rack dehydrators used mostly for cherry tomatoes and apples, but they worked magic on the mushrooms. I tried slicing them, for a nice presentation and quick drying. Then I got lazy and put the caps in whole – they dried beautifully. I vacuum-sealed them and stashed them in the pantry for winter use.

When the cutting and inoculation season rolled around late last winter I ran into Julie Winslow at the post office, and she offered to include me in her spring order. She informed me that she had abandoned loose sawdust spawn in favor of “thimble spawn” – sawdust spawn packed into little thimble-shaped divets in a plastic sheet that are capped with styrofoam circles. The caps render wax-sealing obsolete and the thimbles take the jamming and punching and special inoculator out of the equation. I was game, and it was easy. Some care must be taken to avoid squashing the plastic cells as you pop the spawn out, but once you get going it is blissfully simple.

We are still re-hydrating shiitakes from the pantry for use in soups and stir-fries, even as the ‘shroom bloom kicks off for another season. Our “old” logs are busting out with shiitakes all over the surface of the logs, and we have a crib of thimble-spawn inoculated logs that are ready to go and starting to pop some button mushrooms out of the inoculation holes. When the logs are “young” they will produce a few mushrooms from the holes where the spawn was planted; after the interior of the log is taken over by the mycelium the mushrooms will emerge all over the log.

There is one aspect of shiitake farming that I haven’t fully figured out. Julie, like most of the shiitake people I know, soaks her logs in giant tubs to force a big fruiting. When I visited her farm she introduced me to the big plastic tubs she uses to soak the logs. They looked like hard koi pond shells. I knew this would be a challenge for us, so I planned to let nature take its course, relying on rain to soak the logs and encourage fruiting. We get enough mushrooms to meet our own needs and probably feed a few more families as well, but the opportunity to try a little soak presented itself. I had filled one of our skiffs with water to locate leaks, and when the water stuck around I sunk as many logs in it as I could fit. After a day or so I put them back in the woods, and they did not explode with mushrooms. I decided it was not worth pursuing this trick further, especially as we do not need to time our blooms for market.

Growing shiitake mushrooms has been a success for us. Setting up the logs is relatively painless if you can source some oak and operate a drill. Thimble spawn makes the process very simple. We ended up using a run-of-the-mill drill. Without a custom bit, a 5/16ths-in drill bit with a wrap of duct tape at the 1.25-inch mark will do just fine. I discovered the duct-tape depth measure while tapping maples for syrup, but that’s another story and the bottom line is that it works. The season for cutting oaks has passed, according to Julie Winslow, who advises cutting the trees before the leaves are as big as a mouse’s ear. I took this year off from inoculating logs, but I plan to resume next spring, as I’m utterly spoiled by the robust flavor and unbeatable freshness of homegrown mushrooms. If you are on Cape and interested in growing some mushrooms, Julie sometimes sells aged, inoculated logs at local farmer’s markets.

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