What to do with a "Spent" Mushroom Kit?

Oyster Blocks: Twice is nice, but is there more where that came from?

grey dove oyster mushrooms

What to do with a "Spent" Mushroom kit?

With ready-to-fruit blocks/tabletop farms, the usual story is as follows:

  1. Open kit and enjoy a substantial first flush and subsequently wow your friends and family with your mycological prowess (never gets old!).
  2. Wait.
  3. Coax a second, smaller harvest out of the block
  4. Rejoice!
  5. Consider waiting for a third flush, but tire of waiting.
  6. Wonder "what if there is more I could do to keep this going?"

Well, thanks to FFP customer Michael Kortlander, we may now have an answer to the question posited in #6 above. Here's his method.

Based out of the noted mushroom cultivation hub of Los Angeles, California, Michael decided to get a little creative and try the 'lasagna' method with the spent block in plastic buckets. Following a strong second flush, he let the block take a well-deserved rest in the refrigerator for a week. He then obtained some organic sawdust and shaved cherry wood, mixed the two together, and poured boiling water over the mix and let it rest overnight.

Then came the fun part: Michael broke up the spent blocks into small handful sized pieces and mixed it in layers with the sawdust/shaved cherry wood mixture in smaller, almost ice-cream bucket sized containers with holes drilled into scattered spots around the buckets (figure 1). He placed these buckets into a closet and let them be. After a week, he noticed mycelium recolonizing the top layer (figure 2), and after three weeks, the entire bucket had been myceliated and oyster clusters were popping and pinning, abundantly (figure 3).

Thank you Michael for sharing this experience and these tactics for extending the life and yield of a standard ready-to-fruit block. Now keep in mind that this method may work with oyster mushrooms, but is quite a bit trickier with other varieties, but we appreciate the intrepid spirit and curiosity!

Other Ideas

If the method above seems a bit technical here are some other options to move your block along.

Option 1: Bury your block. And by "bury" we mean mulch it in with wood chips or sawdust in a shaded location. While you'll get far better results with a fresh block, doing this with a "spent" block can sometimes bring out another flush and, as a bonus, requires no additional work from you. Simply mulch in your block and let Mother Nature take it from there. If you're growing kits in the winter, bag them up and place them in your garage or refrigerator and opt to mulch in the spring of the year when the ground warms up. Mushrooms respond to temperature and humidity swings, so your best time to start looking for additional fungi is in the spring and fall of the year. Keep in mind that this works better with certain varieties, but for the cost of some wood chips it's worth the experiment!

Option 2: Enrich your compost. Have you ever heard of "mushroom compost"? It's the latest rage in the composting world! Spent mushroom blocks are still rich in mushroom mycelium. And while that mycelium may not be able to convert any more sawdust to mushroom fruiting bodies, that myceliated sawdust substrate adds a bonus fungal punch to your compost pile.

Option 3: Throw them in a hugelkultur bed.If you haven't read our blog "Using Mushrooms in Hugelkultur", this would be an excellent opportunity to check it out! In this guest blog we learn that oyster mushrooms are a great addition to hugelkultur mounds. While typically you would want to use fresh spawn, jamming sections of a spent kit into crevasses might achieve similar results! And if it doesn't, the mound is still a nice final resting place for that mycelium.

Related Videos:
Take it a step further:
Make your own mushroom kits with this DIY block kit! Oyster DIY Block Kit
Keep in mind...
While this can be done with an "expired" kit, you can use the same process with spawn. Spawn will provide healthy, vigorous mycelium that isn't tired from producing mushrooms. If using a kit, do make sure to keep it refrigerated until you are ready to expand it into your buckets!

Buckets being reused for mushroom cultivation.

Figure 1

Oyster mycelium colonizing substrate.

Figure 2

Michael's mushrooms!

Figure 5

Buried oyster block

oyster mushroom buried