How to Grow Reishi Mushrooms

How to Grow Reishi Mushrooms on Supplemented Hardwood Sawdust

How to grow reishi mushrooms starts by sterilizing hardwood sawdust at 15 PSI for 150 minutes, inoculating at 10 percent grain spawn, and holding carbon dioxide below 2,000 ppm to form conks. Sealing the bag and restricting air exchange gives you tall finger-shaped antlers instead, which is a legitimate morphology but a very different yield profile.

I have been growing reishi for 15 years at Out-Grow, and the single mistake I see repeated across home grows is cutting the bag open before the block has fully colonized, which aborts pins and sets the whole flush back a month. Reishi is a slow wood-rot polypore that punishes shortcuts and rewards patience. The steps below exist because I have watched what happens when any one of them gets skipped.

Reishi Mushroom Cultivation Equipment Check List

1. Step 1 Choose Your Reishi Mushroom Substrate Ingredients

   What You Need

   • Hardwood sawdust or hardwood fuel pellets, 8 lbs dry
   • Wheat bran, 0.9 lbs
   • Rice bran, 0.22 lbs
   • Food-grade gypsum, 0.22 lbs

   What To Do

   Reishi is a white-rot lignin decomposer, which means it pulls its food from the woody polymers in hardwood and will not colonize straw the way oyster mushrooms do. Pick a hardwood that is dense and high in lignin. Oak is the gold standard in my shop because it gives the heaviest yields, but sugar maple, beech, and sweetgum all work well. Stay away from anything coniferous for Ganoderma lucidum, including pine, cedar, and spruce, because resin compounds in softwood will stall the mycelium. If you only have conifer, grow Ganoderma tsugae, the hemlock reishi, which is a different species.

   Your supplement blend should be capped at 25% of total dry weight. Any higher and you are building a perfect home for contamination instead of reishi. The wheat bran and rice bran provide nitrogen and minerals, and the gypsum buffers pH toward the acidic range the mycelium prefers.

   
   

   Hardwood	Colonization Speed	Typical Yield	Notes
   Oak	Moderate	Highest	Industry standard. Dense lignin, long productive life.
   Sugar maple	Moderate	High	Very reliable. Second only to oak.
   Beech	Fast	High	Good choice if you want faster spawn run.
   Sweetgum	Fast	Moderate	Decomposes quickly. Shorter flush cycle.
   Pine / cedar / spruce	Will not colonize	None	Resin blocks mycelial growth. Do not use.

   → Ready for Step 2 when you have a weighed dry pile of sawdust plus wheat bran, rice bran, and gypsum in front of you, every ingredient measured to the gram.

2. Step 2 Mix and Hydrate the Reishi Mushroom Substrate to 65 Percent Moisture

   What You Need

   • Weighed dry ingredients from Step 1
   • Filtered or distilled water, 2.7 to 3.2 liters
   • Large clean mixing tub or 5-gallon food-grade bucket

   What To Do

   Combine the dry sawdust, wheat bran, rice bran, and gypsum in a clean tub. Mix thoroughly so the bran and gypsum distribute evenly. Uneven supplementation is one of the most overlooked causes of patchy colonization, because any pocket with heavy bran ends up nitrogen-rich and attracts Trichoderma before the mycelium reaches it.

   Add water in stages. Pour in roughly two-thirds, mix for a full minute, then add more a cup at a time until the substrate hits 65% moisture by weight. The squeeze test is reliable once you have done it twice: grab a handful and squeeze hard. A few drops of water should run out of your fist. No water means too dry. A thin stream means too wet, and you need to add more dry sawdust.

   
   
   

   Target pH is 5.5. Reishi mycelium measurably peaks in biomass around pH 5.0 and tolerates up to 7.5, but performance drops hard toward neutral. The gypsum you mixed in handles most of the buffering, so you rarely need to adjust further unless your water is hard.

   → Ready for Step 3 when a squeezed handful of substrate releases two to four drops of water, holds together briefly, then crumbles when you open your hand.

3. Step 3 Fill and Sterilize the Reishi Mushroom Blocks at 15 PSI

   What You Need

   • Hydrated substrate from Step 2
   • Autoclavable filter patch grow bag, gusseted
   • Pressure cooker or autoclave rated to 15 PSI

   What To Do

   Scoop the hydrated substrate into the fruiting block bag until it holds roughly 5 pounds wet weight. Press the substrate down gently to knock out air pockets but do not pack it so hard that water squeezes out the bottom. Fold the top of the bag in thirds to keep the filter patch clear during sterilization. Let the bag sit undisturbed for 12 to 24 hours before you sterilize. That rest period lets any bacterial endospores germinate so they are vulnerable during the heat cycle. Skipping this step is why some growers lose three blocks in a row to slimy bacterial wet-rot.

   Load the bags into your pressure cooker and add about two inches of water to the bottom. Vent the cooker for 10 to 15 minutes with the petcock open before you seal it. This matters because cold air trapped inside the chamber does not transfer heat the way saturated steam does, and if you skip the vent you end up sterilizing the outside of the bag while the center stays below 100°C. Once you see a steady column of steam, close the petcock and bring the cooker up to 15 PSI at 121°C. Hold that pressure for a minimum of 150 minutes for a 5-pound supplemented sawdust block.

   
   

   Load	Pressure	Time at Temperature
   Liquid culture or agar plates	15 PSI / 121°C	30 minutes
   Quart grain jars	15 PSI / 121°C	120 minutes
   5 lb grain bag	15 PSI / 121°C	180 minutes
   5 lb supplemented sawdust block	15 PSI / 121°C	150 to 180 minutes

   Let the cooker depressurize on its own. Do not force it. A large block holds heat for hours and can take up to 8 hours to cool to room temperature, and inoculating a block above 90°F kills grain spawn on contact. Patience here saves you a whole batch.

   → Ready for Step 4 when the bag feels cool to the back of your hand and a thermometer against the outside reads under 80°F.

4. Step 4 Inoculate the Cooled Reishi Mushroom Blocks With Grain Spawn

   What You Need

   • Cooled sterilized block from Step 3
   • Reishi grain spawn, 70 g per block (about 10% of dry weight)
   • Still-air box or laminar flow hood
   • 70% isopropyl alcohol spray
   • Impulse sealer or zip ties

   What To Do

   Move the cooled block and your grain spawn into the still-air box. Spray your arms, the outside of the spawn bag, the outside of the block, and the inside walls of the still-air box with 70% isopropyl alcohol. Wait a full minute for the alcohol to evaporate before you open anything. Break up the colonized grain inside its bag with your hands until the kernels move freely and no clumps remain. You want each grain acting as a separate point of attack on the substrate.

   Open the block bag by peeling the folded top back. Pour the loose grain onto the top of the substrate, then massage the bag from the outside until the grain distributes through the full block. Uneven spawn distribution is the difference between a 10-day colonization and a 25-day colonization, because each dead zone has to be reached by mycelium growing in from the edges. Fold the top of the bag back up, press the air out through the filter, and seal with an impulse sealer or fold and zip-tie the neck.

   
   
   

   A commercial grower at 3% spawn rate can get away with less grain because of climate control and laminar flow, but for a home setup you want 8% to 15% of dry weight. One 1-pound grain bag reliably inoculates six 5-pound blocks at a 10% rate.

   → Ready for Step 5 when the block is sealed, the grain is visibly scattered throughout the substrate from all sides, and the filter patch is clear.

5. Step 5 Incubate Your Reishi Mushrooms in the Dark at 75 to 82°F

   What You Need

   • Dark incubation space, 75 to 82°F
   • Heat mat or seedling warming tray if your ambient temperature is below 70°F
   • Hygrometer

   What To Do

   Place the inoculated block in a dark, warm space. A closet, a cabinet, or a dedicated incubation tote all work. Target 75 to 82°F for a North American home setup. Research-grade operations push as high as 82 to 95°F to speed colonization, but above 95°F bacterial activity starts to outcompete the mycelium and you lose the block. Stay under 90°F indoors and you are fine.

   Keep the block in total darkness if you can. Reishi tolerates some ambient light during colonization but strong light can trigger premature pinning before the mycelium has finished claiming the substrate, and those early pins abort. Ambient humidity of around 80% is plenty. The filter patch handles gas exchange, and reishi tolerates carbon dioxide up to about 5,000 ppm during the spawn run, so you do not need fresh air exchange at this stage.

   Expect 7 to 25 days for full colonization depending on temperature, spawn rate, and substrate density. A block at 80°F with 10% spawn runs in about 14 days in my experience. You know it is done when the block is uniformly white from end to end with no visible brown spots of uncolonized substrate and the mycelium is starting to bruise into the first faint reddish or yellowish patches on the surface.

   
   

   Stage	Temperature	Humidity	CO₂	Light
   Incubation	75 to 82°F	~80%	Up to 5,000 ppm	Dark
   Pinning	82°F	95%	1,500 ppm	>800 lux
   Cap formation	82°F	80%	1,000 ppm	Indirect
   Maturation	77°F	60%	Ambient	Indirect

   → Ready for Step 6 when the block is uniformly white throughout, with no remaining brown substrate visible and the first red-brown pigment spots beginning to form on the surface.

6. Step 6 Initiate Pinning by Cutting the Top of the Reishi Mushroom Bag

   What You Need

   • Fully colonized block from Step 5
   • Sanitized sharp knife or scissors
   • Fruiting space with controlled temperature, humidity, and light

   What To Do

   Move the colonized block to your fruiting chamber. Set the space to 82°F, 95% relative humidity, and provide at least 800 lux of indirect light on a 12-hour cycle. Light at this stage signals the mycelium to start forming primordia. Reishi does not pin in darkness the way some species do, and a block left in a closet will sit inert for weeks.

   Cut the top of the bag with a sanitized knife, leaving about two inches of bag above the substrate. If you want flat red conks, you want fresh air reaching the substrate, so make a wide horizontal slit. If you want antlers, keep the bag sealed and make only a small slit or leave it closed entirely. I have seen growers ruin a beautiful colonized block by cutting it wide open at 60°F in a dry basement, then wondering why pinning never started. Temperature, humidity, and light are what trigger the shift out of vegetative growth.

   Within 5 to 14 days you should see the first primordia, small white nubs that darken into red-brown knots over the next few days. Those nubs are the pins that will become your mushrooms.

   
   

   → Ready for Step 7 when small white nubs appear on the substrate surface and begin darkening to red-brown within three to five days.

7. Step 7 Decide Between Antlers and Conks by Managing CO₂ During Fruiting

   What You Need

   • Pinned block from Step 6
   • Fresh-air exchange source (fan, passive vents, or open chamber) for conks
   • CO₂ meter if available (helpful but not required)

   What To Do

   This is the single most important decision in reishi cultivation and it is almost entirely driven by carbon dioxide. Elevated carbon dioxide tells the mushroom to keep reaching for fresh air, which produces the tall finger-shaped antler form. Low carbon dioxide tells the mushroom that fresh air is already here, which lets it lay down a flat cap and form the classic red lacquered conk shape. The number that matters is roughly 2,000 ppm. Below that threshold with active air exchange, you get conks. Above it with the bag sealed or mostly sealed, you get antlers. This is the one decision I see home growers get wrong more than any other.

   Pick your target before you move the block, because switching late produces malformed mushrooms that are neither a clean antler nor a properly capped conk. If the pins are already antler-style and you want conks, let them grow to 2 to 3 inches tall inside the sealed bag, then cut the bag open and move into active fresh-air exchange. The antlers will flatten on top and form caps.

   
   

   Form	CO₂	Effort	Yield	Best For
   Antler	>5,000 ppm, sealed bag	Low	Lower	Tinctures, teas, visual display
   Conk	Below 2,000 ppm, open bag + FAE	Higher	Higher	Dried slices, bulk processing
   Mixed / malformed	Fluctuating	Frustrating	Variable	Fix your environment. Pick one and stick with it.

   → Ready for Step 8 when the pins have committed to a clear morphology, either elongating upward as antlers or laying down horizontally as cap primordia.

8. Step 8 Mist and Light the Reishi Mushrooms Through Cap Formation

   What You Need

   • Fruiting block from Step 7
   • Clean spray bottle with boiled-and-cooled or distilled water
   • Indirect light source, 10 to 12 hours per day

   What To Do

   Mist the inside of the bag or the fruiting chamber two to four times per day. Use boiled-then-cooled water or distilled water, because chlorinated tap water and stagnant water pick up bacteria that cause pin abort and cap spotting. Do not spray the fruiting bodies directly. Aim at the walls of the chamber or the sides of the substrate. A heavy spray right on a young cap causes yellow bruising that never heals.

   Keep the fruiting space at 82°F and 80% relative humidity during active cap expansion. As the caps begin to thicken and reach full size, drop the temperature to about 77°F and the humidity to 60%. That step-down pushes the mushroom from growth mode into maturation mode and produces the deep lacquered red the species is known for. Indirect light for 10 to 12 hours per day is enough. Direct sun on the block will cook the surface and stall the grow.

   
   
   

   Expect 30 to 45 days from the first pins to fully mature conks. Antlers finish faster, typically 20 to 30 days from pinning, because they are not building a cap structure.

   → Ready for Step 9 when the white growing margin at the cap edge shrinks and the cap surface turns fully reddish-brown with a wet, lacquered shine.

9. Step 9 Harvest Your Reishi Mushrooms Before Spore Release

   What You Need

   • Mature mushrooms from Step 8
   • Sharp serrated knife or heavy scissors
   • P100 respirator if harvesting conks at full maturity
   • Paper bags or clean flat tray for transport

   What To Do

   Watch the white growing edge on the cap margin. When it shrinks from a clear white band down to a thin line and the cap surface is uniformly deep reddish-brown, you are at peak harvest. If the margin yellows and you see a fine rust-colored powder appearing on the cap or the surrounding bag, the mushroom has begun releasing spores. Reishi produces one of the heaviest spore loads of any cultivated mushroom, and an unprotected harvest in a small indoor space will coat every surface and trigger respiratory irritation that lingers for days. Wear a P100 mask whenever you are near a sporulating reishi, and cover nearby surfaces with paper you can throw away.

   Cut each mushroom at the base of the stem with a sharp serrated blade. Reishi flesh is leathery and tough, and a dull knife will shred the base and damage the mycelium at the surface of the block. Leave no stub behind, because stubs rot and invite contamination into the substrate before the second flush.

   
   

   Block Size	First Flush Fresh Yield	Dried Weight	Total Flushes
   5 lb supplemented sawdust block	8 to 16 oz fresh	3.5 to 7 oz dry	2 to 3
   1 kg dry substrate reference	~250 g fresh (25% biological efficiency)	~112 g dry	2 to 3

   → Ready for Step 10 when the mushrooms are cut clean from the block and transferred onto a clean tray for drying.

10. Step 10 Dry and Store Your Reishi Mushrooms for Long-Term Use

    What You Need

    • Harvested mushrooms from Step 9
    • Food dehydrator or low oven, capable of 95 to 115°F
    • Airtight storage container with desiccant packet or oxygen absorber

    What To Do

    Reishi is never eaten fresh. The tissue is woody and bitter, and fresh caps spoil within days. Slice the caps while they are still pliable, ideally within two hours of harvest, into roughly quarter-inch strips. Thicker slices dry unevenly and trap moisture that becomes a mold problem later.

    Run the dehydrator at 95 to 115°F for 12 to 24 hours. Do not exceed 122°F because the heat-labile triterpene compounds that give reishi its characteristic bitter flavor and medicinal profile start breaking down above that threshold. Properly dried reishi snaps cleanly when you bend a slice. If it flexes, it is still too wet and needs another four to six hours. Final moisture should be 3 to 5%.

    
    
    

    Store the dried slices in an airtight jar with a desiccant packet or an oxygen absorber. Keep the jar cool and dark. Properly dried and sealed reishi holds its potency and flavor for a year or more. For very long storage, pack in sealed polyethylene bags at 2 to 5°C in a refrigerator.

    → Ready for Step 11 when slices snap cleanly and feel cool and bone-dry to the touch, then are sealed into a dry airtight container.

11. Step 11 Rest the Block for a Second Reishi Mushroom Flush

    What You Need

    • Harvested block from Step 9
    • Clean water for rehydration
    • Same fruiting chamber settings from Step 6

    What To Do

    After the first harvest, return the block to pinning conditions, 82°F, 95% humidity, 1,500 ppm carbon dioxide, and bright indirect light. If the block has lost significant weight, submerge it in cold clean water for 8 to 12 hours, then drain it and return it to the chamber. Cold shock plus rehydration is the signal that typically kicks off the second flush. Pins usually reappear within 10 to 15 days.

    Expect two to three total flushes from a supplemented sawdust block before the substrate is exhausted. Yield drops with each flush, so the second flush is smaller than the first, and the third is smaller still. Once the surface turns greenish, orange, or slimy, the block is done and should be composted or discarded. Do not try to keep a contaminated block alive. It will spore out your fruiting chamber and infect every block you have in progress.

    → Cycle complete when you have harvested your final flush and the block is ready to compost.

Troubleshooting Common Problems When Growing Reishi Mushrooms

Green Mold (Trichoderma) Contamination When Growing Reishi Mushrooms

Trichoderma shows up as a fast-spreading powdery green patch that starts white for the first day or two and then turns bright forest green as it sporulates. It almost always means one of two things: the block was not sterilized long enough, or the substrate was too wet and low in oxygen. The fix is prevention. Hold 15 PSI for a full 150 minutes on a 5-pound block, do not skip the 12 to 24 hour rest before sterilization, and target 65% moisture rather than the 70% some guides suggest. Once you see green on a block, the block is gone. Seal it in a trash bag and remove it from the room before the spores spread, and wipe every surface with 70% isopropyl alcohol before you open another block.

Bacterial Wet-Rot When Growing Reishi Mushrooms

Bacterial wet-rot looks and smells unmistakable. The substrate turns slimy, grey or yellowish, and gives off a sour or foul odor. It is almost always a sterilization failure: cold air was not vented from the pressure cooker before pressurization, or the block was over-hydrated, or both. The 12 to 24 hour rest before sterilization matters most here because it lets bacterial endospores germinate into their vulnerable vegetative form. Without that rest, endospores survive the full heat cycle. Once a block is bacterial, there is no saving it. Discard the block, scrub your pressure cooker, and revisit your venting procedure.

Cobweb Mold When Growing Reishi Mushrooms

Cobweb mold shows up as a fine, wispy grey-white growth that looks fuzzier and more three-dimensional than healthy reishi mycelium. It moves across the surface fast, often a full inch per day, and it tends to appear in fruiting chambers where humidity is stuck above 95% with stagnant air. The fix is air movement. Add a small fan for passive fresh-air exchange, drop humidity to 85% for 24 hours to break the cycle, and mist less frequently. Cobweb mold on an early pin is usually recoverable if you react fast. On a mature conk it often means the flush is finished and the block should be moved toward second-flush rest.

Antlers Forming When You Wanted Conks When Growing Reishi Mushrooms

This is not really a contamination problem, but it is the single most frequent complaint I hear from new growers. The block produces tall finger-shaped growths that never flatten into caps. The cause is carbon dioxide, full stop. Antlers form when carbon dioxide stays above about 2,000 ppm, which happens when the bag is sealed, the fruiting space has no air exchange, or the chamber is too small for the number of blocks inside. The fix is to cut the bag wide open across the top, move the block into a space with active fresh-air exchange, and let the antlers lay down and form caps over the next two to three weeks. Alternatively, embrace the antler form intentionally. It makes a fine tincture and takes less work.

Pins Aborting Before Cap Formation When Growing Reishi Mushrooms

Aborted pins look like small red-brown nubs that turn black or grey, shrivel, and fall off the substrate. The two most common causes are a humidity drop below 80% during pinning, or a temperature spike above 85°F that cooked the young primordia. Stabilize your chamber first, bring humidity back up to 95%, drop temperature back to 82°F, and hold steady for at least 72 hours. Remove the dead pins with clean tweezers so they do not rot into the substrate. New pins usually form within 7 to 10 days if the block is otherwise healthy.

How to Grow Reishi Mushrooms: Frequently Asked Questions

How long does it take to grow reishi mushrooms?

Q. How long does it take to grow reishi mushrooms?

A. From inoculation to first harvest takes 8 to 16 weeks on indoor supplemented sawdust blocks. Spawn run runs 7 to 25 days, pinning takes another 5 to 14 days, and cap formation to mature harvest takes 30 to 45 days. Outdoor log cultivation takes 9 to 18 months before the first flush. Temperature is the main variable that moves the timeline.

How long do reishi mushrooms take to grow compared to other mushrooms?

Q. How long do reishi mushrooms take to grow compared to other mushrooms?

A. Reishi is one of the slower cultivated mushrooms. Oyster mushrooms finish in 2 to 4 weeks, lion's mane in 4 to 6 weeks, and shiitake in 8 to 12 weeks indoors. Reishi runs 8 to 16 weeks indoors and up to 18 months on logs outdoors. The slow pace is normal for a dense wood-decomposing polypore.

How do you grow red reishi mushrooms?

Q. How do you grow red reishi mushrooms?

A. Red reishi grows on the same sterilized hardwood sawdust process described above, using a red reishi strain (Ganoderma lucidum or Ganoderma resinaceum). The deep red lacquered cap color develops during maturation when you drop temperature from 82°F to 77°F, reduce humidity from 80% to 60%, and maintain fresh-air exchange below 2,000 ppm carbon dioxide for conk form.

What temperature and humidity do reishi mushrooms need?

Q. What temperature and humidity do reishi mushrooms need?

A. Reishi mushrooms need different conditions at each stage. Incubation runs 75 to 82°F at 80% humidity. Pinning needs 82°F and 95% humidity. Cap formation runs at 82°F and 80% humidity. Maturation shifts to 77°F at 60% humidity. The step-down produces the hard red lacquered surface the species is known for.

Can you grow reishi mushrooms at home?

Q. Can you grow reishi mushrooms at home?

A. Yes. A beginner can grow reishi mushrooms at home with a pressure cooker rated to 15 PSI, a still-air box, filter patch grow bags, hardwood sawdust, wheat bran, gypsum, and reishi grain spawn. A first-time grow typically costs 75 to 150 dollars in equipment plus 15 to 25 dollars per block, and yields 8 to 16 ounces of fresh mushroom per 5-pound block.