Fruiting Block Kits FAQ

Fruiting block kits are mushroom grow kits, but tend to be larger (5 lbs) and some require a bit more care depending on the species. They come bagged rather than boxed, and we recommend growing them in a fruiting chamber such as a monotub or a martha tent setup like our BoomRoom. A controlled environment produces the best results, and since these kits are larger, they can yield more than our Spray & Grow Kits.

Oyster and lion's mane fruiting block kits are great for beginners — they're reliable producers and require the least amount of effort. Reishi is also excellent for beginners because the mushroom grows inside the unopened bag, with no special care or fruiting chamber required.

Our fruiting block kits are made from sawdust blocks amended with substrate supplements.

For most species, leave the block in the bag for the entire growing cycle. There are two exceptions:

Shiitake should be removed from the bag before going into the fruiting chamber. Nameko should have most of the top of the bag cut off — leaving about 4″ of plastic above the block — before going into the fruiting chamber.

Optimal temperature ranges are listed on each fruiting block kit product page under "Temp, Humidity & CO2 Guide," found below the product description.

Harvesting guidelines are listed on each fruiting block kit product page in the "Growing instructions" section under "Harvesting your mushrooms."

All kits should produce at least one flush, and with a little patience you can often get a second or third depending on species. After harvesting your first flush, remove any remaining growth from the block and follow the method that matches your setup:

Martha tent or automated fruiting chamber: Leave humidity and fan running and wait about 2 weeks for new pins to form.

Monotub or non-automated chamber: Open twice daily and spray blocks generously with water. Keep exposure brief to reduce contamination risk.

No fruiting chamber: Cover the block with a humidity tent made from a large plastic grocery bag with many small quarter-sized holes. Remove it twice daily and spray the blocks generously with water.

Be patient: It's normal for each subsequent flush to take longer to appear. If there's no progress after two weeks, soak your block.

Soaking: Remove the block from the bag and submerge in cool water for 20 minutes. Lion's mane only needs 5–10 minutes as it tends to break apart if soaked too long. After soaking, let the block drain cut-side down for 10 minutes, or tip it to let excess water run off. Pat dry with a towel before returning to the bag.

A very vigorous kit — totally normal. For oysters, lion's mane, pioppino, or chestnut, you can ignore mushrooms fruiting inside the bag. If they're easily accessible, feel free to break them off and compost them.

For shiitake, pinch off and compost any premature pins when you remove the bag.

It's not unusual for fruiting blocks to crack or crumble in transit. If you receive a broken kit:

1. Remove the kit from the shipping box and unfold the top of the bag to create air space. Do not open the bag.
2. Check that the filter patch is not obstructed — this lets the organism breathe and continue to thrive.
3. Place the bag in a dark spot at room temperature (60–70°F) and don't move it around.
4. Allow the mycelium to recover undisturbed for up to 10 days.
5. When you see mycelium re-growth and/or mushroom pins, your kit is ready to go.
6. Follow the growing instructions for your specific species.

Chances are it's not mold — it's mycelium. Your kit contains an amended sawdust block with mushroom mycelium growing through it, which may appear as a soft, white, mold-like covering. That's healthy and normal. Some species show more prominent mycelium than others — lion's mane tends to be fine and faint, while oyster mycelium can develop into a thick, leathery mat.

If you're unsure, reach out with a photo and we'll help you identify what's happening.