How to Grow Shiitake Mushrooms

Shiitakes are one of our favorite things to grow in our backyard garden. They provide us with much-needed vitamin D and rich umami flavor in the cold winter months. Even some experienced gardeners are intimidated by the prospect of growing mushrooms, but as I’ll outline below, shiitakes can actually be a very straightforward and satisfying part of your garden repertoire.

Materials

At the most basic you really only need two things to grow shiitake mushrooms: mushroom spawn and suitable wood. It also helps to have tools to drill holes or cut up your wood and insert the shiitake spawn—more on that later. Shiitake spawn can be produced at home, but you need laboratory-like conditions to consistently produce healthy uncontaminated spawn. We source our shiitake spawn from a small family-owned supplier called Field & Forest, and have always been happy with their products.

The best types of wood to grow shiitake mushrooms on are oak, sugar maple, sweetgum, and beech. Other hardwood trees will work as well, but in our experience they typically produce fewer mushrooms over time. To avoid contamination from other wood-eating fungi your wood needs to be sourced from a living tree. Though this doesn’t mean you need to kill a healthy oak tree to grow shiitakes. We have been growing mushrooms for years, and we have never once cut down a tree to source wood. Most mature hardwood trees have branches that are the perfect diameter for cutting into mushroom logs. Serendipitously, these branches are often hanging inches above critical infrastructure.

We source our logs by looking out for arborists who trim them around power lines in the late fall and winter. Often they are happy to have us haul the limbs away because it saves them a bit of work. The reason we source them in fall and winter is that this is when the trees are dormant and storing nutrients in their wood instead of their buds and leaves. These stored nutrients will contribute to larger shiitake crops and logs that produce for longer periods of time.

Growing Conditions

Just like animals, plants have an immune system to protect them from diseases like viruses, bacteria, and fungal infections. Given that we are trying to infect our wood with shiitake mushroom fungus, we need to give the cut logs a few weeks for their immune system to taper off before introducing the shiitake mushroom spawn. After about two to three weeks from cutting, the wood will be a perfect environment for the shiitake fungus to thrive and it’s time to inoculate your logs.

There are a few methods for inoculating shiitake logs, but the most common for home gardeners is to drill holes in the log every 6 inches and hammer in small wooden dowels that contain the spawn. After hammering in the dowels, it’s best to seal them with melted bee’s wax to prevent them from drying out. Another option is to cut your logs into 1-foot chunks and stack them with layers of sawdust containing shiitake spawn sandwiched between each section. This method works best for wider logs that can sit up on their own without toppling over.

Once your logs are inoculated, you need to give the mycelium time to colonize the entire log before it starts producing mushrooms. Depending on the variety of shiitakes you choose to grow and your weather, this can take anywhere from 6 months to a year and a half. You’ll know the logs are close to producing when you can see some of the mycelium forming white blotches on the ends of the logs.

Once your logs are fully colonized and starting to produce mushrooms you can either sit back and allow them to fruit naturally when conditions are right, or you can shock them into producing on command. Many shiitake varieties can be forced to fruit by submerging them in cold water for 24 hours and then returning them to their normal conditions. This “shocks” the log into producing mushrooms. If you are going to use this method make sure to give them at least 4 weeks between each fruiting to avoid overtaxing them.

Pests

Shiitakes in general are very pest-free crops though there are a few critters to look out for. Slugs and snails absolutely love mushrooms. Thankfully they’re pretty slow creatures, and if your mushrooms are only fruiting every once in a while, the slugs and snails often won’t find them before you harvest your crop. Another pest to look out for is fungus gnats. These little flies lay their eggs in the gills of mushrooms, and their larvae tunnel through the caps. In my experience, they only become an issue if you leave your mushrooms on the logs long past their optimal harvest time. As long as you harvest your shiitakes when the caps are still tender pests shouldn’t be an issue.

Harvest and Use

Once your logs are producing mushrooms, the hard work is over and it’s time to sit back and enjoy the fruits of your labor for the next few years. We check on our logs every couple days in the growing season and when we see little mushroom caps starting to form we know to come back in a couple of days to harvest them.

You can either twist them off the log or cut their stem with a knife to harvest. If you don’t plan to eat them right away you can store them in the refrigerator for about a week, but make sure not to store them in plastic as this will suffocate them and cause them to turn slimy. We have about 24 logs in our garden which is far more than we could eat fresh, so we dehydrate our mushrooms when they are producing heavily in the spring and fall which allows us to eat homegrown shiitake mushrooms all year round.