Mushroom Plugs: How Do They Work?

Mushroom plugs are an easy and low-maintenance way to grow mushrooms at home. They are commonly used to inoculate logs and stumps to produce gourmet and medicinal mushrooms. The plugs are made from wooden dowels, usually birch, that are inoculated with mushroom mycelium and then inserted into pre-drilled holes in logs or stumps. The mycelium then grows through the wood, eventually producing mushrooms. This method is suitable for small projects and beginners as it requires no special tools and can be done with a small number of logs.

Making mushroom plugs at home

Mushroom plugs are the most basic way to grow mushrooms on logs. It's a natural choice for small projects because it is easy to use, requires no special tools, and is available in small quantities. Here is a step-by-step guide to making mushroom plugs at home.

Step 1: Prepare the hardwood dowel pins

Soak your hardwood dowel pins in water overnight. The length of the log will determine the number of dowel pins required. For an 8-inch thick log that's about 3 feet long, use about 50 mushroom plugs.

Step 2: Prepare the jar

Fill a quart-sized canning jar halfway with the soaked hardwood dowel pins, add about 4 tablespoons of uncooked brown rice, and add 1/2 cup of water. Make sure there is about 2 inches of space for things to expand. Drill a small hole in the jar lid and tape over it with paper bandage tape.

Step 3: Pressure cook the jar

Put the lid on the jar and pressure cook at 15 psi for one hour. Allow everything to cool to room temperature, drain the excess water, and add 1 milliliter of liquid mushroom culture. Put the lid back on and let it sit for a few weeks.

Step 4: Prepare the plugs

When you begin to see fluffy white mycelium growing on the rice, shake up the jar to help distribute the mycelium throughout the plugs. Once all the plugs are covered in mycelium, they're ready to use.

Step 5: Prepare the log

Cut or acquire a fresh hardwood log, approximately 4 to 6 inches in diameter and 4 feet long. Hardwood, such as oak, maple, and elm, is preferred, but the best type depends on the kind of mushrooms you are growing. Drill holes in the log using a 5/16-inch drill bit, spaced 4 to 6 inches apart, and allowing 2 inches between rows. The holes should be about a quarter-inch deeper than the length of the plugs and a bit wider.

Step 6: Insert the plugs

Insert the spawn plugs into the holes and use a hammer to gently tap them into the log. The plugs should be flush with the surface of the log.

Step 7: Seal with wax

Melt beeswax or cheese wax and pour it over each hole to seal the plugs in the log. This will prevent the spawn from drying out and keep critters out. You can also seal both ends of the log with wax using a paintbrush.

Step 8: Store the log

Stack the logs crisscross-style in a shaded area with good air circulation. An area under trees is preferred as it tends to remain moist. Elevate the stacks above the soil on old logs or flat stones to prevent soil contact and insect pest infestations. Keep the logs moist by watering them during dry spells.

Depending on the mushroom variety, it may take 6 to 18 months for the mushrooms to mature. Once the mushrooms start fruiting, you can harvest them by pulling them down by the stems or cutting them close to the bark with a sharp knife.

Drill holes into logs

To grow mushrooms on logs, you'll need to start by drilling holes into the logs. The holes should be about 1-¼” deep, or just deep enough to fully take in the plug. It is recommended to use an 8.5mm bit with a stop or a 5/16" drill bit. You can use any power drill with a suitably-sized wood bit, but you want a tight fit between the dowel and the log. Try to clear the remaining sawdust and woodchips from the holes to make room for the plugs.

When drilling the holes, it's important to choose the right type of log. Many types of hardwood will work, including aspen, birch, poplar, oak, maple, beech, and hornbeam (ironwood). In general, avoid softwoods like spruce, pine, and fir, as well as fruit trees. The tree species is important when selecting logs, as different species of trees will work better for different species of mushrooms. Make sure to use untreated hardwood and ensure that the wood is not from a dead or unhealthy tree. Summer or fall inoculation is recommended when using plug spawn, and it's best to cut logs as close as possible to the inoculation date.

Once you've drilled the holes, you can move on to the next step of pounding the mushroom plugs into the holes.

Insert plugs into the holes

Inserting plugs into the holes is a straightforward process, but it requires attention to detail to ensure successful mushroom growth. Here are the steps to follow:

First, it is important to select the appropriate wood for your plugs. Choose hardwood trees such as aspen, birch, poplar, oak, maple, beech, or hornbeam (ironwood). Make sure the wood is untreated, fresh, and cut close to the inoculation date, avoiding dead or unhealthy trees.

Next, drill holes into the logs or stumps using a power drill with a suitable drill bit size. The drill bit should be slightly smaller than the dowels to ensure a tight fit. The holes should be about 1-1/4" deep, or just deep enough to accommodate the entire plug. Clear the sawdust and wood chips from the holes to make room for the plugs.

Now, it's time to insert the plugs. Use a hammer or mallet to gently pound the plugs into the holes until they are flush with the bark. The plugs should be snugly fit and difficult to push in by hand. This step ensures that the mycelium can colonize and penetrate the log effectively.

Finally, seal the inoculation points with wax to prevent the spawn from drying out. You can use paraffin wax, beeswax, or cheese wax for this purpose. Heat the wax until it becomes malleable, and then place a generous amount over each hole.

By following these steps, you'll create an ideal environment for the mycelium to grow and produce mushrooms. The time it takes for the mycelium to fully colonize the log can vary from 6 months to 2 years, depending on various factors such as wood type, amount of plug spawn used, weather conditions, and log size.

Seal the holes with wax

Once you have drilled the holes and hammered the plugs into the logs, the next step is to seal the holes with wax. This is an important step as it prevents the spawn from drying out before the mycelium gets a chance to grow. You can use paraffin wax or beeswax for this purpose.

First, heat the wax until it is soft and malleable. You want it to be soft enough to spread easily. Then, place a generous amount of wax over each hole, covering it completely. This will protect the inoculation points and seal in the moisture needed for the mycelium to grow.

It is important to use enough wax to create a tight seal. The wax will act as a barrier, preventing the plugs from drying out and ensuring the optimal conditions for mushroom growth. Make sure to press the wax down gently around the hole to remove any air bubbles and create a smooth, sealed surface.

The wax will eventually harden, creating a protective layer over the inoculation site. This layer will safeguard the plugs from drying out and ensure the mushrooms have the best chance of thriving. Sealing the holes with wax is a simple yet crucial step in the process of growing mushrooms with plugs.

Types of mushrooms to grow

Mushroom plugs are an easy and low-maintenance way to grow mushrooms outdoors. The process, called log cultivation, involves inserting mycelium-infused hardwood dowels (or plugs) into holes drilled into freshly cut logs or stumps. The mycelium will start producing mushrooms after a full year and can continue to do so for up to five years.

There are several types of mushrooms that can be grown using this method, and the type of mushroom will determine the kind of wood you should use. Here are some of the most common mushrooms to grow using plugs:

Shiitake

Shiitake mushrooms have a longer incubation period and may take nine months to two years to produce mushrooms. They grow well on hardwood species such as alder, birch, oak, maple, cottonwood, and beech.

Oyster

Oyster mushrooms are a great species to start with as they produce mushrooms from spring to fall. They also prefer hardwood species like alder, birch, oak, maple, cottonwood, and beech.

Lion's Mane

Lion's Mane mushrooms can be grown on natural logs using plug spawn. They are relatively distinct in appearance, making them easier to identify when harvesting.

Reishi

Reishi mushrooms are another variety that can be cultivated on natural logs using plug spawn. They are also relatively distinct, reducing the risk of mistaking them for other varieties.

Other Varieties

In addition to the mushrooms mentioned above, there are several other types that can be grown using plugs, including Comb Tooth, Nameko, Olive Oysterling, Chestnut, and Turkey Tail.

Frequently asked questions