I’ve often been asked about how to grow shiitake mushrooms, and since I’ve never posted about it, here it is.
Start with a young hardwood forest in need of thinning. Alder is what I have around here, but lots of different hardwoods will work, especially oaks. I look for logs that aren’t too crooked, and about 4-8″ in diameter. This year, I thinned a couple of acres of pure alder that I have, which was way, way more than I needed for mushroom logs. The rest will go to firewood, and my remaining trees should grow faster and larger now.
The best time to cut the trees is in the winter or very early spring, definitely before sap starts to flow. Once they are starting to leaf out, you’re a little on the late side. When processing your logs, be careful not to bang up the bark. Trees with sap running tend to get the bark damaged very easily. I cut the logs right where the tree falls and carefully carry and load them by hand.
In the past I used to cut my logs at 42″, because that was the size of a standard pallet, and I used to stack my logs on pallets. Now I just throw a couple of un-inoculated logs on the ground and make my stacks on those. So this time I cut my logs at 48″. Much longer gets hard to handle, though. Make sure the logs are straight and relatively uniform, without damage or rot. I also take the time to scrub off all the moss and other stuff growing on them. If you have a pressure washer, this can go pretty fast. Some people wash and scrub them down to clean bark without any lichens left on it at all, but in my experience, they don’t need to be perfectly spotless.
Since alder is a wood that rots easily, the alder tree has some defense mechanisms against invading fungi. Alder will encapsulate and “wall off” any rot very effectively, and right after you cut or damage an alder tree, it produces an antifungal compound of some kind, so I always stack my freshly cut logs in the woods for a couple of weeks or so before inoculating them, to let this defense mechanism run its course.
Keep the logs cool and in the shade, while you’re waiting for your spawn to arrive in the mail, and while you’re working on them. We lost over 100 logs one year because I had not learned this lesson yet. Logs that sit in the sun get sunburned, which makes the bark less useful for shiitake mushroom growth, but worse, the logs warm up and grow Trichoderma, a locally prevalent, aggressively competing fungus. If that stuff gets a toehold before the shiitake can get established, then the logs fail to ever produce mushrooms. So keep your logs cool and in the shade!
I order my spawn from Northwest Mycological Consultants in Corvallis, OR. I generally grow one of the cold weather strains, as they tend to tolerate my benign neglect, they fruit on natural cycles well, and the resulting mushrooms are of extremely high quality. This year, I also bought a wide range strain, that has a longer fruiting season than the cold weather strain I usually grow. Timing wise, I usually order my spawn about the time I take down the trees.
I use sawdust spawn, rather than plugs. This requires a special tool for inoculating, which you can also order from NMC. I also ordered the special hardened drill bit from them, and it has drilled several thousand holes now with no troubles. Regular hardware store bits will not do that.
The other huge time saver is the drill. Don’t even bother with a regular shop drill, or cordless drill. You’ll be drilling holes for days that way. What you want is a high speed angle grinder, and to make a simple adapter so that you can mount a drill chuck on it. This is a way, way faster way to drill a lot of holes without hassle. Put a stop collar on your drill bit so you don’t make the holes super deep.
You want the holes to be a little bit deeper than the length of the plug of spawn that you’re putting in there. You want there to be a little bit of open space at the bottom of the hole underneath the spawn. You also want to be careful to not tear up the bark too bad when drilling holes. Pull the drill straight out so that it doesn’t snag and tear the bark around the edge of the hole. I put the holes about 3-4″ or so apart and several full length rows around the circumference of each log. More is better for fast, successful colonization, but too many holes wastes spawn and leaves you with fewer logs. At the rate I generally do it, a five pound bag of spawn will inoculate about 20-25 logs.
I’ve found that laying the logs out in the grass to drill them is easier than trying to drill them on the bed of the truck, or on the sawhorse set up that we use for inoculating on. Having some teenagers around to move logs for you is nice…
Inoculating is pretty straightforward. Open the bag, shove the tool into the spawn, it will fill with spawn, then put the tool over a hole and depress the plunger. Voila! Spawn is now inside the log. Repeat several hundred times…
Once you have a pile of inoculated logs, now it’s time to seal the holes with wax. We use a small thrift store slow cooker to melt wax in and keep it hot. There’s a million ways of doing the wax, too, but since we’re small time and usually only do up 50-100 logs at a time usually, we just use paint brushes. The wax protects the spawn from invasion by pests, and from drying out.
Now write the strain number on the ends of the logs so you can keep track of which is which. I used to not do this, and then got frustrated when some logs performed better than others, but I couldn’t say for sure which was which. It only takes a few minutes and a big sharpie to label them.
Then stack them under some conifer shade, so that they have good airflow, but no direct sun beating down on them. They’ll take all summer to fully colonize the logs, and it will probably be the following spring at least before you see any mushrooms. You can get more production by soaking the logs and managing them more intensively. There’s a lot of great information in the “Shiitake Growers Handbook”, by Paul Przybylowicz and John Donoghue.
My last batch of successful logs were inoculated in 2008, and were still producing mushrooms as of a couple of weeks ago. If I had forced fruiting, though, it would have used them up faster. My 2011 logs were invaded by Trichoderma and have never fruited. I have a good feeling about today’s batch, though. I think these will be successful.