Cultivating Garden Giant Mushrooms
1. Storing Your Spawn Block(s)
Congratulations on your new spawn! We hope you are looking forward to collaborating with the mycelium of Stropharia rugosoannulata. It is an excellent addition to any landscape, and when well cared for, will produce several flushes (harvests) of garden giant (a.k.a. wine cap) mushrooms.
Store your block(s) unopened in a cool dark place until you are ready to use them.
2. Building an Outdoor Bed
a. Choosing a Location
While your spawn is incubating, it's a good idea to assess where in your yard you would like to install your mushroom beds. Although Stropharia mycelium can tolerate direct sunlight and summer heat, your mushrooms will retain more moisture and freshness if you provide them with some amount of shade.
You may also consider where the natural flow of water output is; a garden giant bed would be super happy at the bottom of a slope, or near a downspout. Regardless, it will need to be watered, so make sure your hose can reach it.
b. Gathering Substrate Materials
The bare minimum in this category includes plain cardboard, fresh hardwood chips (a mix of softwood would also suffice), and spawn. You may also use untreated dead leaves, coffee grounds, straw, food scraps, and other yard waste. Stropharia mycelium is extremely hardy and loves a microbially active environment.
c. Determining Bed Size
Decide how large you would like your beds to be. One spawn block can cover a 4 x 4 square foot area. The more space you cover, the more mushrooms you will get. You can also integrate your spawn into an existing garden bed; simply combine spawn + woodchips and spread it amongst your veggies. The fruiting bodies may not be as large but the symbiosis between your plants and the mycelium will be more than worthwhile.
d. Building the Bed(s)
Put down plain cardboard as a barrier. Then layer spawn, woodchips, and other substrate materials on top of it. If available, add a thick layer of straw to the finished bed to lock in moisture. Thoroughly water the bed immediately after installation and daily for two weeks. After that, weekly watering is sufficient.
e. Adding a Casing (optional)
After 4-6 weeks, your beds will be ready to fruit. Around this time, some cultivators will add a thin layer of rich, microbially active compost, otherwise known as a casing, to their garden giant beds as a final nutrient boost. Stropharia is somewhat unique in this preference, and it is not entirely necessary, but you may want to experiment with it if you can.
f. Overwintering Your Beds
To put your mycelium into hibernation at the end of the growing season, cover your beds with a fresh layer of wood chips (and straw, if available). If avalable, use burlap bags or tarp to cover your beds. The following spring, begin watering again for another year of fruiting!
g. Introducing Worms to Make Compost (optional)
Worms absolutely love to munch on myceliated substrate. Once your beds have finished fruiting after 2 years, you might want to consider introducing red wigglers to your garden giant beds. They will consume and digest any remaining mycelium (along with whatever it's growing on) and you will be left with rich, black gold myco-vermicompost.
3. Harvesting, Storing & Cooking Your Mushrooms
Once your mushrooms begin to fruit, they will grow to full size within 3-5 days. Be sure to harvest them while they are fresh; otherwise, they may dry out, or, if it's rainy, become infested with bugs. Harvest by reaching all the way to the base of the mushroom and gently pulling up and to the side. Trim any dirty spots with a knife and cook right away or store in the fridge for up to 10 days.
The stem of garden giant mushrooms is stringy and tough like asparagus. The caps are much softer and are great for making stuffed mushrooms. Overall, their flavor is umami and reminiscent of potatoes. They will go well in any dish or feature nicely as a main ingredient. Enjoy!!
Other Resources: Check out this video from Mushroom Mountain, DIY Mushroom Cultivation by Willoughby Arevalo, or Organic Mushroom Farming and Mycoremediation by Trad Cotter.