Mushroom Plugs: Do They Work?

Mushroom plugs are an effective way to grow your own mushrooms at home. This method of mushroom cultivation mimics how mushrooms grow in the wild. The process involves drilling holes into logs or stumps and inserting mushroom plugs, which are laced with mushroom mycelium, into the holes. The mycelium will start producing mushrooms after a full year of growing and can continue to produce for five years or more. While this method requires some understanding of how mushrooms grow, it is a low-tech and low-maintenance way to have fresh mushrooms in your backyard.

The best types of wood for mushroom plugs

Mushroom log cultivation is a low-tech, ancient method of growing mushrooms that mimics how they grow in the wild. Mushrooms in the wild grow on dead trees, decomposing organic matter to obtain nutrients.

When choosing the right wood for mushroom plugs, it is important to match the mushroom type to the tree variety. Each mushroom species has its own preferences, and matching the mushroom to the correct log species will produce a higher and more consistent yield.

Oaks and hard maples are the preferred wood types for most mushroom species. This is because they are very dense and offer plenty of nutrition for a longer, sustained fruiting period. Other hardwood tree species such as alder, birch, cottonwood, and beech are also good options, especially for Oyster and Shiitake mushrooms.

It is also important to consider the health of the tree. Logs from already decaying trees may have other species of fungi growing in them, meaning more competition for your mushroom spawn. Fresh, healthy trees are better for your mushroom plugs. The best time of year to inoculate logs with mushroom plugs is in late winter when the logs have higher concentrations of sugar. Logs should be inoculated within 4 weeks of cutting, or no later than a month or two, to avoid competition from other fungi.

How to prepare the wood

To prepare the wood for mushroom plugs, you'll need to select the right type of wood, cut it to the appropriate size, and drill holes for the plugs.

Firstly, it's important to choose the right type of wood for your mushroom variety. Most edible mushrooms grow on deciduous, hardwood trees. While softwoods like poplar will produce mushrooms faster, they don't yield as much. Oaks and hard maples are the preferred wood types for most mushroom species due to their density and nutritional content. Other hardwood options include alder, ash, birch, bitternut, cherry, chestnut, hophornbeam, ironwood, maple, oak, pecan, sweet gum, sycamore, tulip poplar, walnut, and willow. Avoid softwoods like spruce, pine, and fir, as well as fruit trees, unless you're growing Pearl Oysters, which prefer maple, or Phoenix Oyster, which prefers spruce.

Freshly cut hardwood logs are ideal, as they should be inoculated no later than a month or two after being cut. Harvest your tree during the fall or winter when their sugar concentration is highest.

Logs should be 4-10 inches in diameter and cut to a consistent length for easy stacking. A suggested length is 2-4 feet.

Once you have your logs, use a power drill with a suitably sized wood bit to drill holes for the plugs. Drill the holes about 4-6 inches apart, creating a diamond pattern or any pattern that ensures a suitable number of holes. The holes should be about 1-1/4" deep, just deep enough to fully take in the plug. Clear the remaining sawdust and woodchips from the holes to make room for the plugs.

The best time of year to inoculate logs

It is best to cut the trees in winter or spring when they are completely dormant and their sugar concentration is highest. Once they've been cut down, the logs should be inoculated as soon as possible. Research at Cornell’s Arnot Forest has shown that winter and spring inoculations are ideal, but summer and fall inoculations also produce sizable harvests.

If you're looking for a fast-growing mushroom species, Oyster mushrooms are a great option. They can be grown on softer hardwoods like tulip poplar and will produce mushrooms from spring to fall. With a shorter incubation period, you can plant them in late winter and start fruiting in the fall of the same year.

The process of inoculating logs typically involves drilling small holes into the logs, packing them tightly with spawn, and then sealing the holes with wax to create optimal growing conditions for the mycelium and reduce contamination by other fungi species. This method of cultivation mimics how mushrooms grow in the wild, feeding on newly dead hardwood. It's a simple and low-tech way to grow your own mushrooms, but it does require some understanding of how mushrooms grow and the specific needs of different species.

How to insert the plugs

To start growing mushrooms using plugs, you'll first need to select the right type of wood. Mushrooms in the wild grow on dead trees, decomposing organic matter to acquire nutrients. Each species has its own preferences, but most mushrooms grow on hardwood from deciduous trees. Preferred hardwoods include oak, maple, alder, elm, chestnut, birch, and beech. Thick-barked hardwoods work best. Logs with thin bark or softer wood will break down faster and won't produce mushrooms for as long.

Once you've selected the right wood, you'll need to drill holes into the log. The holes should be about 1-¼” deep, or just deep enough to fully take in the plug. Use a drill bit that is nearly the same size as your dowel, so you get a nice tight fit with the mushroom plug. Clear the remaining sawdust and woodchips from the holes to make room for the plugs.

Next, you'll need to inoculate the log by pounding the dowels into the holes. They should be too tight to push in by hand, but can be gently pounded in with a hammer or mallet. To prevent the plugs from drying out, cover the freshly inoculated holes with wax. Paraffin wax, beeswax, soy-based wax, cheese wax, or any food-grade wax will work. You can use mud if you don't have any wax. You need just enough wax to cover the plug and make a good seal.

Finally, place the inoculated log in a shady area under a dense forest canopy or under a shade cloth or burlap sack. Do not use plastic as this will encourage mould and bacteria growth. The logs should not be in contact with the soil to prevent competitor fungi from invading the logs.

How to care for the logs after inoculation

After inoculating your logs, you will need to place them in a shady area under a dense forest canopy, or cover them with a shade cloth or burlap sacks. Do not use plastic, as this will encourage mould and bacteria growth. The logs should not be in contact with the soil, as this will allow competitor fungi to invade the logs. Criss-cross the logs to stack them.

The logs should be placed in a location where temperatures are consistently above freezing. If you inoculated during the winter, allow the logs to colonize for a minimum of 30 days in temperatures above 40 degrees Fahrenheit. You can do this by storing them indoors or in a warmer location.

The logs need to maintain good moisture content for the healthy growth of the mushroom mycelium. You can use mud or wax to retain the moisture in the logs. Cover at least one cut end of the log with wax or mud to prevent moisture loss. If you live in a very dry environment, you can cover both cut ends. For stumps, cover the cut stump face. Do not cover the entire log or stump, as you still want to allow moisture to enter the log from rain or watering.

Once a log has "flushed" (produced a crop of mushrooms), it should be allowed to "rest" for at least 10 to 12 weeks. This provides the mycelium (roots) with time to replenish the energy required for fruiting.

Frequently asked questions