How to Grow Shiitake Mushrooms on Logs: A Simple Step-by-Step Guide

Mushrooms are nutritious and versatile food. While there are many varieties of mushrooms, shiitakes are especially well known, both for their health benefits and their distinct flavor.

What many don’t know about shiitakes is how easy they are to grow. Growing shiitake mushrooms on logs take minimal work and a small investment, making them perfect for new cultivators.

And after your mushrooms fruit, you’ll be able to enjoy delicious shiitakes for up to six years, without ever stepping foot in a grocery store. Lets do it!

What You Need:

• Hardwood logs
• Shiitake plug spawn (50 per log) or sawdust spawn
• Drill
• 5/16 drill bit (for plug spawn)
• 3/8 drill bit (for sawdust spawn)
• Drill bit stop collar
• Rubber mallet
• Food-safe wax (optional)
• Daubers brush or paintbrush (optional)
• Hose or other watering implement
• Hay, wood pallet, or bricks
• Wood ash (optional)

About logs: Growing shiitake mushrooms is typically done on oak logs (the word “shiitake,” in fact, means mushroom of the oak (1)). If you cannot source fresh oak logs, other hardwoods like alder, ash, aspen, birch, beech, hickory, hop hornbeam, maple, and poplar can also be used. Logs for growing shiitake mushrooms should be between 4-6 inches across, and 40 inches long.

How To Grow Shiitake Mushrooms on Logs:

1. Prepare Your Shiitake Mushrooms Logs

Shiitake mushrooms need fresh, clean logs to grow. Ideally, you’ll be able to cut tree limbs and gather them yourself from trees on your property. If you’re able to use your own tree, choose one that is healthy and has no other fungal growth. Try cutting the trees in the fall when the sugar content in trees is at its highest. This extra sugar will help to promote the growth of your shiitake mushrooms.

Once you’ve cut your logs, lean them against each other off the ground (try using a pallet or bricks to give them a boost) to season for about three weeks.

Using logs from your own land is unfortunately not always practical or possible, so you may need to purchase logs and limbs from a woodlot. Timber farms, treelots, and tree-removal companies can all direct you to a reliable source of fresh wood.

But no matter where you source your wood from, make sure it is freshly cut with bark intact. Do not use anything that is live, green, deadfall, or growing any form of lichen or fungi (2).

It may be tempting to skip the manual labor or a trip to the woodlot and collect fallen limbs out in the wild, but logs that have been sitting out may already have other fungal growth or disease. If you do not have access to fresh logs, try purchasing a pre-inoculated shiitake mushroom grow log instead. These logs are already prepared with spawn and can even be kept indoors.

2. Inoculate Your Logs

Inoculation is the process of introducing the mushroom spawn to the growing medium. For beginning mushroom-growers, plug spawn is the easiest way to inoculate a mushroom log. Plug spawn consists of wooden dowels that have already been inoculated. These can be easily inserted into a log with a mallet. Alternatively, sawdust spawn can be used to inoculate a log but it is more difficult and requires a specialized tool. Either of these spawn types, as well as other growing supplies, can be bought at mushroom supply stores like https://northspore.com/.

To inoculate your logs with plug spawn, use a 5/16 drill bit with a stop collar set to make inch deep holes. For sawdust spawn, use a 3/8 inch drill bit and set the depth to 1 ¼ inch. Starting 2 inches from the top of your log, drill holes every 8 to 10 inches, stopping when 2 inches remain. Start your second row 2 inches from the first and stagger your next set of holes to create a diamond pattern. Do this all the way around the log, then tap the plugs in with a mallet, or pack in sawdust with an inoculator tool.

To help retain moisture, you can plug the holes you made with food-safe wax such as beeswax, cheese wax, or specialty mushroom wax. Melt the wax in an old pot or bowl and spread it over hole openings with a paint brush or daubers brush.

Pro-Tip: It’s better to over-inoculate than under-inoculate. While you may spend a bit more money on spawn, leaving too much extra space can allow competing fungi to colonize the logs.

Incubate your Shiitake Spawn

Your shiitake logs need to incubate for 6-12 months before they can start fruiting. Over the course of those months the logs will need regular watering, unless the temperature is below freezing. At least an inch of rain or supplemental water is ideal, though more water is advisable when the weather is extremely hot. In moist climates, you’ll need to provide 10 minutes of watering per week when there hasn’t been a strong rain. In dry climates, you’ll need to double or triple this. For your convenience, consider how easily you can reach your logs with a hose when you choose where to store them.

In addition to water access, consider sunlight and evenness of terrain when you choose an incubation spot. The best places for shiitake mushroom logs are shady and off the ground. This type of environment promotes water retention and prevents competing fungal growth. A bed of hay or wooden pallet placed next to a fence or behind a tree is a great area to stack your logs either log-cabin or teepee-style.  

In addition to natural shade, a breathable fabric cover is a useful tool to keep a stack of shiitake logs out of the sun while still allowing water to filter through. Do not use a plastic tarp or any other water-repellent material for this, or your logs may grow mold that could kill or infect your shiitakes. 

Initiate Fruiting

After 6-12 months of incubation, shiitake logs will, on occasion, begin to grow mushrooms on their own. Usually, though, growing shiitake mushrooms on logs requires a shock to initiate fruiting. To ensure a strong colony, wait until at least 9 months have passed since inoculation before you start the shocking process.

Shocking shiitake spawn into fruiting can be done with water or physical strikes, depending on your personal preference and access to water. These methods imitate the natural conditions (e.g., heavy rainfall or a tree falling) that induce fruiting in wild mushrooms. For water shocking, soak the logs for 24 hours straight, ideally in non-chlorinated water. This can be rainwater, cooled boiled water, a pond, or hose water in a large tub. To physically stimulate fruiting via strike, you can hit the logs with a heavy pipe or bat or drop the logs lengthwise.

Once you have soaked or hit your logs, bring them to a shady spot where they can stand upright, not stacked. Leaning them against a fence or wall will ensure they stay standing so you can monitor all around each log for growth. You can use the same bed of hay or wood pallets previously used to keep the logs off the ground.

If slugs are a concern, surround the logs with a 3-inch ring of wood ash after they’ve been placed upright. Over the next few days, keep the shiitake logs moist by watering for five minutes at a time once or twice a day (3).

Harvest Your Shiitake Mushrooms

It can take anywhere from 2 days to 2 weeks for the beginnings of mushrooms, called primordia, to appear. Once your shiitake mushrooms have grown their round brown caps, you can pick them any time before the caps flatten completely. Younger, smaller mushrooms will be more tender than ones that have been left to mature.

If you’d like bigger yields try this indoor method for growing shiitake mushrooms

When picking your mushrooms, protect the mycelium by using a sharp, clean knife to cut the shiitake off the log at the base of its stem. Twisting the mushrooms off the log by hand can damage the mycelium and negatively impact future growth.

For a visual guide to harvesting, this video by Cherry Valley Films can show you what a perfectly ripened shiitake mushroom looks like:

Once you’ve harvested your shiitake mushrooms, the logs will continue to produce new fruit if properly maintained. Keep watering your shiitake logs 2 to 3 times a week when temperatures are above freezing, shock the logs again after five weeks, and you will be rewarded with a new flush of mushrooms. This cycle can be continued for up to 6 years and stopped once the logs grow mould or the mushroom quality decreases.

Pro-Tip: You can increase the Vitamin D content of your shiitake mushrooms immediately after harvesting them if you lay them out in the sun, caps down, for 24 to 48 hours. 

Want an even simpler way to grow mushrooms at home? Try a mushroom growing kit. It’s beginner-friendly and doesn’t require any tools.