Supplemented sawdust blocks

What it is

This is what most specialty mushroom growers fruit from: sawdust or hardwood fuel pellets mixed with a supplement such as wheat bran or soybean hulls. It needs steam sterilisation and a lab for inoculation, and it gives the highest yields of the common methods¹.

Master’s mix is the grower name for a 50/50 blend of hardwood sawdust and soybean hulls, credited to T.R. Davis of Earth Angel Mushrooms². GroCycle’s guide hydrates it to about 60% and pressure-sterilises it for 2.5 hours at 15 psi². The same guide warns that the high share of soy hulls raises the chance of contamination and says it is not the best substrate for shiitake because its nitrogen is too high². Shiitake is usually grown on a sawdust and bran mix instead.

If you do not want to sterilise, you can buy ready-to-fruit blocks. Cornell notes that shiitake, lion’s mane, chestnut and pioppino blocks fruit well outdoors in the warmer months, and advises against fruiting oyster outside because insects lay larvae in them¹.

What it suits

Most specialty species. Cornell lists oyster, shiitake, lion’s mane, chestnut, maitake, reishi and king oyster on sawdust, and pioppino on blocks¹.

Species notes are on the species page; for the mushrooms themselves, see Ohio Gourmet Mushrooms.

Equipment

• Hardwood sawdust or hardwood fuel pellets
• Wheat bran or soybean hulls
• Filter-patch bags
• Pressure cooker or steriliser large enough for the bags
• Grain spawn, still air box or flow hood, heat sealer
• Shelving with space between bags

Time to first harvest

10 days to 12 weeks of incubation. Cornell gives incubation times of about 10 to 20 days for oyster on sawdust, about 21 days for most specialties, and 42 to 84 days for shiitake¹. Shiitake also needs another 4 to 5 weeks after full colonisation to "popcorn" and brown before it is moved to fruit¹.

Contamination and other risks

• Contamination from the rich supplement, especially at high soy-hull ratios².
• Heat. The core of a 5 or 10 lb bag can run 10 to 15 °F above room temperature; Cornell keeps incubation under 80 °F and leaves a hand’s width between bags¹.
• Green mould on soaked second-flush blocks if their outsides are not allowed to dry first¹.

Steps, in overview

1. Mix and hydrate. Combine sawdust or pellets with the supplement and water.
2. Bag and sterilise. Fill filter-patch bags and pressure-sterilise; GroCycle uses 2.5 hours at 15 psi for master’s mix².
3. Inoculate. Add grain spawn in a clean space and shake it through the bag¹.
4. Incubate. Around 70 °F, never above 80 °F, with space between bags¹.
5. Initiate. Cut oyster, chestnut and pioppino bags corner to corner; cut small Xs for lion’s mane; open king oyster at the top¹. Shock shiitake by soaking 5 to 12 hours or chilling 12 to 24 hours¹.
6. Fruit and harvest. Give humidity, fresh air and light, and harvest every day once mushrooms mature¹.

Common mistakes

• Moving or chilling shiitake blocks during browning, which makes them fruit early and cuts yields¹.
• Letting shiitake blocks touch, so they do not popcorn in those spots¹.
• Using master’s mix for shiitake².
• Fruiting lion’s mane from the top, where water gathers and invites disease¹.