How to Grow Berkeley's Polypore (Bondarzewia berkeleyi)

• 1 lb dry rye berries or whole wheat berries
• Water for soaking and simmering
• 1 polypropylene grain bag with 0.2-micron filter patch (or wide-mouth quart mason jar with filter lid)
• Pressure cooker capable of 15 PSI

Scale-up: 3 lbs grain = 3 bags · 5 lbs grain = 5 bags

Rinse the grain, then submerge in cold water and soak for 12 hours. Drain, rinse again, then add to a pot of fresh water and simmer for 15–20 minutes until kernels are swollen and just tender but not splitting. Drain and spread on a clean surface or baking rack to surface-dry for 30–60 minutes — kernels should feel dry and separate to the touch, moist inside but with no visible moisture on the exterior. Load into grain bags and seal each bag by folding the top and securing with a heat seal or zip tie. Sterilize at 15 PSI for 90–120 minutes. Allow bags to cool completely to room temperature — at least 8 hours — before proceeding.

Out-Grow sells Berkeley's polypore liquid culture ready to inject.

• Berkeley's polypore mushroom liquid culture syringe (10–12 cc per 1 lb grain bag)
• Cooled, sterilized grain bag(s) from Step 1
• 70% isopropyl alcohol, alcohol lamp or torch
• Still air box or laminar flow hood
• Nitrile gloves, face mask

Work inside a still air box or under a laminar flow hood. Wipe the injection port of each bag with isopropyl alcohol. Flame-sterilize the needle until it glows, let it cool for 3–5 seconds, then inject 3–5 cc of Berkeley's polypore mushroom (Bondarzewia berkeleyi) liquid culture per 1 lb grain bag through the self-healing injection port. Remove the needle, wipe the port again, and set the bag upright in a dark location at 70–75°F.

• Inoculated grain bag(s) from Step 2
• Dark, stable space at 70–75°F

Keep inoculated grain bags in darkness at 70–75°F. Shake bags gently after the first visible mycelium appears to break up the colonized grain and redistribute growth — this speeds even colonization. Do not open bags during this phase.

• 4 lbs hardwood sawdust (oak/maple) — hardwood fuel pellets re-hydrated work well
• ¾ lb (about 1¾ cups) wheat bran
• Approximately 5½ cups water, added gradually to field capacity
• 1 polypropylene substrate bag with filter patch, 5 lb capacity

Scale-up: 3 blocks = multiply by 3 · 5 blocks = multiply by 5. Out-Grow also carries wood-based substrate bags ready to inoculate if you want to skip mixing.

Combine sawdust and wheat bran in a large mixing bin. If using hardwood fuel pellets, add the water first and let pellets hydrate and break down for 20–30 minutes before mixing in the bran. Add water gradually, mixing thoroughly, until the substrate reaches field capacity — squeeze a handful firmly; only a few drops should fall, not a stream. Load into substrate bags, leaving 4 inches of headspace. Seal and sterilize at 15 PSI for 120 minutes. Cool completely for at least 12 hours before inoculating.

• Fully colonized grain spawn bag(s) from Step 3
• Cooled sterilized hardwood sawdust substrate bag(s) from Step 3
• Still air box or laminar flow hood, isopropyl alcohol, nitrile gloves

Inside your still air box or flow hood, squeeze and knead the colonized grain bag thoroughly — work the bag until all grain kernels separate completely from each other and no clumped masses remain. Open both the grain bag and substrate bag. Pour the broken-up grain spawn evenly across the surface of the sawdust substrate, distributing it across the entire top surface before mixing. Mix until no visible pockets of grain are isolated from substrate and grain is distributed evenly throughout. Seal the substrate bag. Do not inoculate warm substrate — ensure it is fully at room temperature.

• Inoculated hardwood sawdust block(s) in sealed bag(s)
• Dark location at 70–75°F

Place sealed, inoculated blocks in darkness at 70–75°F. Keep the bags sealed throughout colonization — the filter patch provides necessary gas exchange. Do not open, mist, or disturb the bags. Bondarzewia berkeleyi colonizes more slowly than common polypores; allow 30–60 days at optimal temperature without assuming failure. Inspect bags visually for contamination — any green, black, or blue mold coloration means the block is compromised.

• Fully colonized Berkeley's polypore mushroom block
• Fruiting chamber, tent, or shotgun fruiting chamber (SGFC)
• Humidifier or misting bottle to maintain ~90% relative humidity
• Thermometer/hygrometer
• Indirect light source (ambient room light is sufficient)

Cut or fold open the top of the bag to expose the block surface to fresh air (FAE — fresh air exchange). Move the block into a fruiting chamber set to 64–75°F. Maintain humidity at approximately 90% throughout fruiting — mist the chamber walls (not the block directly) twice daily if using a manual setup, or run an ultrasonic humidifier on a timer. Provide indirect ambient light — direct bright light is not required and is not documented as beneficial for Bondarzewia berkeleyi. Maintain steady temperature; drastic swings outside the 64–75°F range are the most common cause of failed pinning.

• Clean, sharp knife or scissors
• Container for harvest

Harvest Berkeley's polypore mushroom (Bondarzewia berkeleyi) while the cap lobes are still thick, firm, and pale cream-to-tan in color. Do not wait for the caps to spread fully and thin out — once the flesh becomes watery, the caps begin to darken to tan or brown, or the texture turns tough when pressed, harvest immediately. Cut the cluster at the base with a clean knife, removing the entire rosette as one mass. Leave the block surface intact where possible to allow recovery for potential subsequent fruiting.