Growing Shitake Mushrooms on Logs, by Dave S.

My absolute favorite mushroom to eat is the shiitake. They are expensive to buy in the store, but the good news is that they are easy to grow at home. These flavorful and meaty delights are one of the most common mushrooms in the world and also the one with the most health benefits. Unlike any green plant, they have all of the essential amino acids. And they are  good source of vitamins. Shiitake mushrooms are great for building your immune system and are antibacterial, antifungal, and antiviral. They are a powerhouse of nutrients and contain about 60% carbohydrates, 20% protein and 10% fiber. They are a good source of B and D vitamins which are tough to find in the plant world.

The word shiitake means “mushroom of the oak”, but it can be grown on several different hardwood logs like sugar maple, beech and ironwood. I have had the best success growing them on red oak logs. I have found that I get a little less production on sugar maple and the taste of the mushrooms seems to be a little more bland on that substrate.

PREPARATION

The first step in the process is to cut and prepare the logs. I look for oak logs that are 4 to 6 inches in diameter, cut from healthy, disease-free trees that have few or no branches coming from them. Thick bark is better than thin bark. I look for logs that have a wide band of sapwood (the lighter color wood between the bark and center heartwood) since this is where the shiitake spawn will colonize. If you are not a physically strong person use logs on the thinner side since they can get quite heavy. The logs must have a fairly high moisture content for the mycelium to propagate, so these logs should be cut from two weeks to two months before they are inoculated and should be cut when the trees are dormant. I cut the logs 36 to 42 inches long (the thinner pieces are cut on the longer side and the thick pieces on the shorter side) and store them in a shady place. Typically I will cut the trees in March here in the Upper Midwest and inoculate them in mid-April. I lay them on old pallets to keep them up off the ground. It is not a problem if they get covered with snow.

INOCULATION TYPES

The second step in to determine which method of inoculation to use. The cheapest method is to use sawdust spawn. The sawdust is inoculated with shiitake mycelium (the fungus that propagates throughout the log), injected into the log with a special tool and then covered with melted wax. The next method is to use plug spawn, which is a wood dowel that has been impregnated with the mycelium. These are tapped into the holes drilled into the log and then covered with the melted wax. The advantage of this method is that it is very easy to do. The disadvantages are that it is a little more expensive, and the logs do take longer to colonize.

The last method is thimble spawn which is kind of a hybrid of the first two. The sawdust spawn is formed into a thimble shaped mass and then covered with a plastic cap (so no waxing is needed). The advantage is that it is very easy to do, and the disadvantages are that they are only available in a few strains, are the most expensive, and generally have to be made to order. I have tried all three methods and I prefer to use the plug spawn.

STRAINS

The third step is to choose the right strain of shiitake spawn to use in your region. They are available in cold, warm, and wide range strains which indicate their fruiting season. Do some research to see what strains do well in your area. I have grown all three here in the upper Midwest and the wide range strains do the best. I’m guessing it would be the best bet in most areas.

PREPARATION

The fourth step is to prepare the logs for inoculation. I like to do this on a nice, dry day, or do it inside. I start off by painting one end of the log with melted wax (this end will be the one I set on the ground after the incubation phase), and any cuts that I may have done to take off small branches. This is done to prevent other organisms from contaminated the log, and also to slow down the drying process. If you are using sawdust or plug spawn you will also need the wax to cover the holes. Cheese wax is the most common type of wax to use, although I use the cheaper unscented paraffin beads.

INOCULATION

The fifth step is to inoculate the logs. Regardless of which method you choose, you will have to drill holes in the log. If you are doing just a few logs at a time, you can get by with a cordless drill using the appropriate sized bit and taped off so that the hole ends up the right depth. For larger quantities you can use an angle grinder with a specially made bit. Since I only do about a dozen logs per year, I use a cordless drill but have found the special bits to be much easier and faster to use. The drilling of all these holes is the most labor intensive part of the whole project. Next you need to get the spawn into the hole.

If you are using the sawdust spawn, you will need to get the spring loaded inoculation tool that makes this job much easier than trying to stuff it in by hand. For plug spawn simply tap the dowel in the hole with a hammer to just below the level of the bark, and cover with wax. A dauber or small paintbrush will work best. For the thimble spawn tap them out of the tray they come in and push into the hole. Since they have a plastic cap there is no need for waxing. Start by drilling holes about every 6 inches along the length of the log. About 2 inches below that, drill holes every 6 inches but they should be in between the first row. When you are finished it should resemble a diamond formation.

INCUBATION

The sixth step is to incubate the logs. This is simply putting them in a spot that is shady, has good air circulation, and is in an area that you can water if there is not enough rainfall. Try to find a spot that is a close to 100% shade as you can get. You can cover the logs with some 80% shade cloth if needed. I put them back on the same pallets I originally stored them on to keep them up off the ground. If it is dry enough that I need to water the garden I also water the logs. I put a sprinkler in the middle of the logs that provides a fine mist and turn it on for an hour or two. This incubation period will last from 6 months to a year depending on a whole variety of inputs.

With inoculation in mid-April, I will generally get a few mushrooms in October, but most will pop up the following spring. When I see the first mushrooms I will move the logs to a spot where I can get them close to vertical. This would be up against a rail or circled around a tree. This allows mushrooms to grow all around the log and also to make them easier to pick. This fruiting run tends to be unpredictable and sporadic so you will need to check on them regularly.

FORCING

If you want to move up the predictably factor you can “force” or “shock” the logs into producing, although this method can only be used with the wide range strains. The logs need to be fully colonized before forcing so typically I would wait until about 14 to 16 months after inoculation.Also, you can look at the end of the log that is not waxed and look for one that is almost covered with white mycelium – this will be your best clue that it’s ready to be forced.

Shocking involves submerging the logs in the coldest water you can find for 24 hours. Our well water here is 48 degrees year round so that is what I use. On warm days I’ll either drain and refill a couple of times, or I’ll leave the hose on trickle the whole time. I use a big cattle watering trough to do this. You should see the first little mushrooms starting to form in 4 to 5 days and pick them in 7 to 10 days. We have an annual family event here every August and everyone loves the shiitake mushroom zip sauce we make so I am just about able to guarantee an ample quantity then.

PICKING

Shiitake mushrooms are ready to harvest based on their growth stage rather than overall size. Look for a fairly flat top and and the top edge should be sightly curled under and the gills showing. I twist and pull the mushrooms to remove them from the log, but you can use a sharp knife. Brush off any dirt and put the mushroom in a basket or paper bag. Do not wash the mushrooms with water! This will make them soft and slimy and they will not store well.

STORAGE

Shiitake mushrooms can be stored for one to two weeks if they are kept in a cold (40 degrees (F) or so), dark and ventilated. I store them in the same paper bag used when I pick them and put them in the refrigerator. For long term storage they can be dried. I use a food dehydrator to get them dry, but not brittle. Put them in a clean, dry glass jar and they will keep for at least a year.

ECONOMICS

There are a huge range of prices and options out there, but I estimate that you can get started with an investment of about $50 that will inoculate 10 logs. This would include the spawn, the cost of a special bit and a pound of wax. I’m assuming that you have access to the logs and have a cordless drill.

If you have made it this far you may be wondering if this is worth all the work. It’s obvious that I do, and here are the reasons:

The home grown mushrooms definitely taste better than the store bought.

Once the initial investment in time and materials has been made, you should realize a total of 3 to 4 pounds of fresh mushrooms per log over the course of about 5 years.

Dried mushrooms are great in soups, stews and roasts over the winter months.

If you have any excess harvest they typically command a premium price of $15 to $20 per pound at farmers’ markets.

I hope I have encouraged you to try growing your own shiitake mushrooms. They are fun to grow and a wonderful addition to your garden. In a survival situation they are great source of vitamins and nutrients. The hard work is at the beginning so if you start an annual plan of inoculating logs you will have at least 4 or 5 years worth of production with little ongoing work.