5 Easy Mushroom-Growing Projects for Your Fall Garden

You don't need to like to eat mushrooms to benefit from their presence in your garden. Mushrooms help break down organic matter in the soil and make it available to the rest of your plants. Indeed, mushrooms are probably already growing in your garden. Anyone who composts, mulches, or adds biomass to their garden is encouraging invisible networks of mycelium—the white fibrous substance that is the main body of a mushroom.

But gardeners can be more intentional about their mushroom growing, and there are plenty of ways to incorporate edible mushrooms into the landscape of your yard. Here are 5 of them.

1. Log Cultivation

The Japanese have been growing shiitake mushrooms (Lentinula edodes) on hardwood logs for centuries, producing around 8,000 tons a year. Log-cultivated mushrooms are prized for their superior flavor and smell, compared to other methods of cultivation. They also have lower water content and higher levels of carbohydrates and energy.

Recent improvements in both cultured strains and inoculation techniques have made this method accessible to the home gardener. All you have to do is simply drill holes in almost any hardwood log, fill those holes with either inoculated hardwood dowels or inoculated sawdust, plug the holes up with wax, and then wait for the mushroom to colonize the log. The larger the log, the longer it will take to colonize and fruit. The smaller the log, the quicker it will fruit but the fewer mushrooms you'll get overall.

It can take roughly 8 months to harvest the mushrooms, but annual harvests can last up to four years on the same log.

2. Mushrooms on Coffee Grounds

Mushrooms will grow on just about any biomass, but the strains you want to grow will have to compete with whatever is out there in the environment and the growing substrate already. Professional cultivators go to great lengths to sterilize their growing medium, often keeping it in airtight, lab-like grow rooms too.

Coffee grounds are a medium that has already been steamed—meaning they should be sterile and ready for inoculation. But they need to be used correctly. You can find many websites recommending growing mushrooms in coffee grounds, but just as studies have shown that caffeine inhibits leafy plant growth, the same applies to mushrooms. Increased levels of spent coffee grounds have been shown to slow mycelial growth and prevent the fruiting of mushrooms.

Yet mixed in a compost with a variety of other types of organic material at no more than 20% of the total compost volume, spent coffee grounds are a good medium for growing mushrooms. To prepare your coffee grounds for mushroom cultivation, use decaffeinated grounds and rinse them thoroughly to leach out the toxins that inhibit growth.

3. Mushrooms on Pizza Boxes

Pizza boxes are usually not recyclable because of the presence of grease on them, but the cardboard is rich in cellulose and lignocellulosic pulp residues that make a great source of food for many mushrooms, including oysters (Pleurotus ostreatus), and the grease actually becomes an asset for the mushrooms, providing an additional source of nutrients for fruiting. The tiny corrugations in the cardboard also create channels for the mycelium to colonize.

Cultivation is as simple as flattening down pizza boxes, soaking them in water, and layering them one on top of the other with mycelium in between. It's important to get a good depth of substrate: no less than six to eight inches to ensure successful fruiting.

4. Woodchip Mulch

Mushrooms help to break down woody biomass and are sometimes used to convert biomass into biogas (methane). They can also be a great addition to your veggie garden. You can inoculate wood chips with king stropharia, aka "Garden Giant," spawn and sandwich it between layers of cardboard six to eight inches deep, and use it as a mulch for tomatoes. As the mushrooms break down the lignin in the wood, they prevent the usual process of nitrogen robbery that can happen as a woody mulch breaks down.

5. Bioremediation

The same uptake process by which mushrooms make beneficial proteins, lipids, carbohydrates, and micronutrients available for human consumption can also be used to clean up pollutants and pathogens.

The mycelia of mushrooms form a tight, web-like structure, not unlike a micron filter, and contain enzymes and acids that make them valuable for eliminating or neutralizing pollutants in contaminated soil and groundwater. Known as mycoremediation, this technique is being used in large-scale environmental remediation projects such as waste-water treatment, landfill remediation, and even EPA Superfund site cleanup.

Mycoremediation can come in handy at home as well. If you have chickens, for example, you can use king stropharia-inoculated wood chips as a mulch in your chicken coop, producing edible mushrooms and breaking down coliforms and other potential pathogens in the process. Mushrooms can also be used to reduce the presence of pesticides and heavy metals in soil to potentially safer levels. Of course, you wouldn't want to eat any of the mushrooms grown as part of this latter process.