So you’re a gardener curious about how to grow mushrooms at home? It’s not as difficult or complicated as you might think and you don’t need any special equipment, so why not give it a try? 

A few years ago, the Puget Sound Mycological Society tasked me with developing a simple and reliable method to grow mushrooms for use as an educational tool to demonstrate the life cycle of mushrooms in a tangible way. The method needed to be robust and dependable, assembled without any complex or sterile equipment, be relatively simple, inexpensive and easily assembled on a picnic bench or classroom desk. 

We chose oyster mushrooms (Pleurotus ostreatus) since they are reputed to be the easiest to cultivate, they grow rapidly and are available in a variety of colors including brown, white, blue, gray, yellow, and even pink. The bonus is that they are also delicious to eat! 

Oyster mushrooms have very basic requirements. They only need a carbon source (wood, paper, straw, etc.), a nitrogen source (coffee grounds, alfalfa meal, rabbit chow, etc.) and, of course, water. 

After a few trials and failures with various materials we settled on pelletized kitty litter made from recycled newspaper as the carbon source and using rabbit chow as the nitrogen source to create the best combination. Conveniently, the supplies are readily available at nearby pet supply stores or online and are reasonably priced. These provide everything needed to grow, and ultimately produce a substantial harvest of mushrooms.

The starter, or “seed” material, we used is called “grain spawn”, sterilized rye grain on which oyster mushroom mycelium is grown. When mixed with the carbon and nitrogen sources, the mycelium then “colonizes” the bag, with time producing the “fruiting bodies” aka mushrooms. Grain spawn is readily available for purchase at a reasonable price through commercial sources.

We assembled the grow bags by adding water to the kitty litter, and when it was absorbed, mixed in rabbit chow and grain spawn, then transferred it to a bag. Newspaper bags, produce bags or any other sturdy plastic bag can be used. We knotted the bag and cut slits for air holes, since fungi need oxygen to grow. 

We then waited for the mycelium to colonize the bag. Three weeks later, baby mushrooms, called “primordia”, pushed their way through the slits. They grew and doubled in size every day and were ready to harvest in about a week. 

Sometimes a second, although smaller, harvest appears in another 2-3 weeks. After the second fruiting, the remaining mycelium in the bags can be re-used to start 4-5 more mushroom kits. 

Here is our current method:

• Place 4 cups of recycled newspaper kitty litter pellets in a clean container.
• Add 4 cups of dechlorinated tap water (or warm water) and mix gently. Let it stand for 10 minutes or so until all the water has been absorbed.
• Add 2/3 cup of rabbit chow and 3/4 – 1 cup of oyster mushroom grain spawn.
• Mix gently but well and transfer into a plastic newspaper bag. Pack the mixture down lightly and tightly knot the bag, leaving no air space at the top.
• Cut 4, 1 inch slits in the bag to allow it to breathe. 
• Place the bag in a darkened room or closet at 60 – 70ºF for 2 weeks. Lower temperatures will discourage the growth of contaminants. Avoid drafty areas or fluctuations in temperature.
• Check the bag after two weeks or so and bring it out into a well-lit room (but out of direct sunlight and away from drafts). and watch the bag.
• After about another week, buttons will appear at or near the slits cut in the bag. If the baby mushrooms form under the plastic, further cut the slits to free them.
• Lightly mist the growing clusters 4 – 5 times a day if possible with a spritz bottle containing dechlorinated water. The clusters will double in size every day. Harvest in 5-7 days. Twist them off and use them in your favorite mushroom dish. If you can’t use them immediately, they can be stored in the fridge for up to 3-4 days.

The cost is nominal at approximately $2.50-3.00 per kit.

If the amounts of materials seem too large or too expensive for an individual, why not make it a group activity and split the bill? Or after some experience with the method, consider holding a workshop or kit making session with your fellow gardeners and share the costs. It’s fun, educational, self-sustaining, and ultimately, very tasty, so give it a try. 

Comments, questions and feedback? Need instruction sheets? Have pictures of nice mushrooms? If so, please contact me! Milton Tam: [email protected].