Most organic gardeners probably don't think about it, but they are already growing mushrooms in their garden.
Anyone who composts, anyone who mulches, and anyone who adds biomass to their garden in any shape or form is encouraging invisible networks of mycelium — which help break down nutrients, and sometimes even form direct reciprocal and symbiotic relationships with plant roots. 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. '
When we caught up with mushroom expert Tradd Cotter to talk about his project promoting mushroom cultivation for disaster relief, we also asked him about some easy fall projects for the home gardener.
The Japanese have been growing shiitake mushrooms on hardwood logs for centuries, and 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 less you'll get overall.
Here's a video of Tradd inoculating logs.
And here he is showing off the fruits of his labors.
Mushrooms on coffee grounds
Mushrooms will grow on just about any old 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 and they often keep them in air-tight, lab-like grow rooms too. If you're lazy like me, that sounds like way too much hard work. Coffee grounds from your local coffee shop, however, have already been steamed — meaning they should be sterile and ready for inoculation. Even better news than this, oyster mushrooms love coffee grounds! Be warned, however, bugs and slugs like coffee grounds too. Cotter recommends growing cold climate oysters which fruit in the spring and fall, when bugs are less active and you stand a chance of getting some for yourself.
Mushrooms on pizza boxes
If you don't have a coffee shop near you, maybe you can find a pizza joint? Cotter tells me that pizza boxes, which aren't considered recyclable because of the grease, make a great source of food for many mushrooms, including oysters. The tiny corrugations in the cardboard create channels for the mycelium to colonize, and the grease actually becomes an asset for the mushroom, providing an additional source of nutrients for fruiting.
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. Cotter recommends no less than six to eight inches to insure successful fruiting. He says Mellow Mushrooms boxes, which are printed using vegetable-based inks, are a personal favorite.
Because mushrooms help to break down woody biomass, they can be a great addition to your veggie garden too. Cotter likes to 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.
Here's a video from Eric Toensmeier showing a king stropharia fruiting in garden mulch:
And here's Cotter explaining why he loves the king stropharia so much:
Mycoremediation with chickens
Finally, as Cotter explained when we interviewed him about his disaster relief project in Haiti, mushrooms aren't just for eating. Because the mycelium (the body of the fungus that grows below ground) forms a tight, web-like structure not unlike a micron filter, it can be a great way of cleaning up pollutants and pathogens. This technique is being pursued for large-scale environmental remediation, but it can also come in useful at home — particularly if you happen to have backyard chickens. Tradd and his wife Olga use king stropharia-inoculated wood chip as a mulch in their chicken coop, producing edible mushrooms and breaking down coliforms and other potential pathogens in the process.