Mushroom Plugs: The Art Of Cultivation

Mushroom plugs are an easy and reliable way to grow mushrooms at home. The plugs are made of hardwood dowels that have been inoculated and colonized with mushroom mycelium. The process of making mushroom plugs at home is similar to making first-generation grain spawn, except that hardwood dowels are used instead of sterilized grain. The plugs are then tapped into holes drilled into logs or stumps, which will start producing mushrooms after a full year.

The process of making mushroom plugs at home

Mushroom plug cultivation is a low-tech and low-maintenance method of growing mushrooms that dates back about 2,000 years. The process involves inoculating hardwood logs with mushroom mycelium, which then colonizes the log over a period of 6-9 months. Once the log is fully colonized, mushrooms will begin to emerge and can be harvested.

To make mushroom plugs at home, you will need hardwood dowels, a power drill with a suitably sized wood bit, a hammer or mallet, and wax. The dowels should be made of plain hardwood, such as oak, maple, elm, aspen, birch, poplar, or beech. These can usually be found at hardware stores, craft shops, or online. The size of the dowels will depend on the size of your log, but they should be big enough to provide sufficient surface area for the mycelium to grow, while also being small enough to fit easily into the holes in the log.

Once you have your dowels, you will need to drill holes into the log about 1¼ to 1½ inches deep, with a bit length of 5/16". The holes should be spaced evenly about 4 to 8 inches apart, with 2 to 3 inches between rows. You may also choose to offset the holes to create a diamond shape. After drilling the holes, tap a spawn plug into each one using a hammer or mallet. Be sure to use only one plug per hole.

Finally, seal the plugs with wax to protect the inoculation points from drying out and to prevent other forms of fungi from disrupting your plug. You can use beeswax, cheese wax, or any other type of wax. Melt the wax and pour it over each hole to completely seal the end of the spawn plug. You can also use a paintbrush to apply the wax.

With your mushroom plugs now ready, simply stack the logs in a crisscross style to ensure good air circulation and place them in a shaded, moist area. The entire log should be kept moist, especially during dry spells. After a full year of growing, the mycelium will start producing fruiting bodies, which can be harvested and enjoyed.

Types of wood used for plugs

The type of wood selected for mushroom plugs is crucial, as different tree species offer varying benefits and influence the mushrooms' growth and flavour. Here's an overview of commonly used woods for mushroom plugs:

Oak: Oak is a popular choice for mushroom cultivation due to its durability and high tannin content. Oak plugs are often used for cultivating shiitake mushrooms, as the tannins in the wood provide the mushrooms with a meaty, savory flavour. Oak is also dense and porous, providing an ideal surface for mycelium to colonize.

Hickory: Hickory wood is closely related to oak and shares similar characteristics, including high tannin levels. It is commonly used for plug-spawn production, especially for shiitake and lion's mane mushrooms. The strong, sweet flavour of hickory smoke is desirable, and it imparts a unique flavour to the mushrooms.

Beech: Beech wood is favoured by mushroom growers for its ability to fruit mushrooms consistently. It has a lower tannin content than oak or hickory but is still dense and porous, providing a suitable environment for mycelium growth. Beech plugs are often used for cultivating oyster mushrooms and lion's mane.

Hardwood Sawdust: While not a specific tree species, hardwood sawdust is often used as a general-purpose substrate for mushroom plugs. It typically consists of a blend of hardwood species, such as maple, ash, and birch. This option is suitable for various mushroom types and is often used by hobbyist growers or those experimenting with different mushroom strains.

A less common but still effective option is poplar wood, which is softer than the previously mentioned hardwoods. It is less dense but still suitable for certain mushroom species, particularly those that favour faster-decaying wood, such as reishi mushrooms.

When selecting wood for mushroom plugs, it's essential to consider the specific requirements of the mushroom species you plan to cultivate. Factors such as tannin content, wood density, and porosity can influence the success of your mushroom garden.

Tools required for making mushroom plugs

Making mushroom plugs at home is a simple process that requires a few tools. Here is a list of the tools you will need:

• Hardwood dowels: These can be found at most hardware stores or craft shops. Make sure to get the correct size for your logs—typically, you will need dowels that are 8.5mm in diameter or 5/16" in diameter and about four to ten inches long.
• Drill: You will need a drill with a 5/16" drill bit to create holes in your logs. A bit stop or a band of duct tape will help you set the correct depth.
• Hammer or mallet: Used to gently tap the mushroom plugs into the holes in the logs.
• One-inch bristle paintbrush: This is needed for brushing away debris and sealing the holes with wax.
• Wax: Used to seal the holes and prevent the spawn from drying out.
• Pressure cooker (optional): If you want to sterilize your plugs, a pressure cooker can be used. However, this step is not necessary since the hardwood dowels have limited nutrition and are unlikely to cause contamination issues.

With these tools, you will be able to create your own mushroom plugs and inoculate your logs to grow mushrooms.

Best time of year to inoculate logs

Mushroom plugs are small wooden dowel colonized with mycelium, the mushroom's "root" network. They are raised in sterile, temperature- and humidity-controlled conditions to ensure their viability. Plugs are the most basic way to grow mushrooms on logs and are ideal for novices or small projects.

The best time of year to inoculate logs is during early spring if the logs have been cut during the winter. You can start inoculating about a month before the average last frost date, provided daytime temperatures are above 40°F. If you're cutting logs during the summer, inoculate them within three weeks so that the logs still have adequate moisture content.

In East Tennessee, the best time to plug logs is said to be February and March because of the weather and the sap run. Logs plugged during this time have produced mushrooms in 4-5 months. However, it is possible to successfully plug logs all year round, as long as the logs are recently cut (within a month) from a disease-free tree.

For summer inoculations, it is recommended to work in the morning and choose a shady spot. The ideal temperature for mycelium growth is around 50°F, which supports the mycelium while keeping the growth of other organisms in check.

After inoculation, logs should be stacked like firewood in a shady area that receives precipitation. If your region has low humidity, you can cover the logs with plastic to retain moisture. After 1-2 months, the logs should be separated to prevent mould from setting in.

How to use mushroom plugs

Mushroom plugs are an easy and low-tech way to grow mushrooms outside, mimicking how they grow in the wild. The method involves inoculating freshly cut logs or stumps with mushroom spawn. Here is a step-by-step guide on how to use mushroom plugs:

Step 1: Choose the Right Wood

Select the right type of wood for your mushroom species. Mushrooms in the wild typically grow on dead trees, decomposing organic matter to obtain nutrients. Different mushroom species have specific tree preferences. For instance, Oyster and Shiitake mushrooms thrive on hardwood trees like alder, birch, oak, maple, cottonwood, and beech. Ensure the tree is healthy and freshly cut, with no signs of decay or other fungi.

Step 2: Prepare the Logs

Harvest your chosen trees in the fall or winter when their leaves have fallen, and their sugar concentration is highest. Soak the logs for 12-24 hours before plugging, but allow the bark to dry before plugging. If the logs are less than ten days old, soaking is not necessary.

Step 3: Drill Holes

Use a drill bit of the appropriate size (typically 5/16" or 7/16" diameter) to create holes in the logs. Start drilling about 1-2 inches from the end of the log, spacing the holes approximately 6-8 inches apart. Create rows of holes about 3-4 inches apart along the length of the log. The number of rows will depend on the log's diameter—aim for one row per inch of diameter. The holes should be drilled to a depth of about 1-1.25 inches.

Step 4: Insert the Mushroom Plugs

Tap the mushroom plugs into the drilled holes using a mallet or hammer. Ensure the plugs are flush with the wood, leaving some space for sealing.

Step 5: Seal the Holes

Seal the holes with wax to prevent the spawn from drying out and to create optimal growing conditions. Melt sealing wax in a crockpot or old pot, and apply it over the holes. Also, wax over the ends of the logs and any areas where the bark was damaged or branches were removed.

Step 6: Provide Shade and Moisture

Place the inoculated logs in a shaded area, such as the north side of a house, and provide shade with an 80% shade cloth or bushes. Keep the logs hydrated, especially after a soaking rain, as this indicates the spawn run is nearly complete.

Step 7: Harvest Mushrooms

Depending on the mushroom and wood species, it can take anywhere from four months to two years for the mushrooms to fruit. Oyster mushrooms have a shorter incubation period, while Shiitake mushrooms may take nine months to two years. Once the mushrooms start to grow, you can expect a productive life of up to five years or more, depending on the log's decomposition rate.

Using mushroom plugs is a simple and rewarding way to grow your own culinary and medicinal mushrooms with a bit of patience and the right techniques.

Frequently asked questions