Mushroom Growing:
Complete Overview for Beginners

Per-Species Temperature and Timing Reference

HDW = hardwood. Incubation temperature is the same (70–78°F) for virtually all species — it is the fruiting temperature that varies significantly. Note that pearl and blue oysters prefer cool fruiting conditions; pink and yellow oysters are warm-weather varieties that require higher temperatures to fruit.

Species Profiles

Oyster Mushrooms (Pleurotus spp.): The correct beginner starting point. Their aggressive mycelium outcompetes most contaminants on pasteurized (not sterilized) straw — the most forgiving combination in the hobby. Pearl and blue oyster fruit in cool rooms (55–75°F); pink and yellow require warmth (75–85°F). Multiple flushes from a single block are typical.

Lion's Mane (Hericium erinaceus): Unique appearance (cascading white "teeth"), mild seafood-like flavor, and significant interest for potential cognitive benefits. Grows on hardwood sawdust blocks. Moderately sensitive to CO₂ — fat, round fruiting bodies indicate poor FAE.

Shiitake (Lentinula edodes): Rich umami flavor, highly valued, and uniquely requiring a cold shock to trigger reliable pinning (see Section 07). The 8–12 week spawn run is the longest of common beginner species — patience is the primary skill this species teaches.

Incubation Phase — Colonization

Fruiting Phase — After Full Colonization

Substrate Guide by Species

Why the Distinction Matters

Bacterial endospores are dormant survival structures produced by certain bacteria (particularly Bacillus species) that resist boiling temperatures. They survive pasteurization and can germinate when conditions become favorable. On high-nutrition substrates (grain, sawdust with bran supplement), these bacteria multiply rapidly and compete with or inhibit mushroom mycelium. On low-nutrition straw, aggressive oyster mycelium colonizes faster than post-pasteurization bacteria can establish — the competition doesn't matter as much.

What Happens If You Use the Wrong Method

• Pasteurizing grain spawn instead of sterilizing: Bacterial endospores survive, germinate after inoculation in the warm nutrient-rich grain, and overwhelm the mushroom mycelium within days. The spawn goes sour — visible as brown or wet-looking grain with an unpleasant smell
• Sterilizing straw: Works, but is unnecessary — pressure cooker time and propane are wasted on a substrate that doesn't require it. Hot water pasteurization produces the same results for oyster mushrooms on straw

Method 1 — Bulk Substrate Inoculation (Grain-to-Bulk)

The most common beginner method. Transfer fully colonized grain spawn to a bulk substrate at a ratio of 10–20% spawn to substrate by volume. Mix thoroughly in a clean environment, then consolidate in a monotub, grow bag, or bucket with drainage holes. The colonized grain acts as inoculation nodes from which mycelium spreads outward through the bulk — the higher the spawn rate, the faster colonization and the lower the contamination window.

Method 2 — Layering (Tray/Tub Method)

Alternate 1–2 inch layers of spawn and substrate in a tray or tub, similar to lasagna layering. Most commonly used for oyster mushrooms in trays or button mushrooms in casing trays. Less thorough mixing than bulk inoculation but suitable for loose substrates where mixing would compact the material and reduce oxygenation.

Method 3 — Log Inoculation (For Outdoor Cultivation)

Drill holes in a diamond or grid pattern across a fresh-cut hardwood log (oak, maple, alder) — holes 4–6 inches apart, 1.5 inches deep. Insert plug spawn or sawdust spawn into each hole, then seal with cheese wax to prevent drying and contamination. Logs take 6–18 months to fully colonize before fruiting. Once colonized, logs fruit multiple times per year for 3–7+ years. Best for shiitake, oyster, and lion's mane outdoors.

For still air box (SAB) construction and use, see Module 07 — Growing Supplies & Tools →

For grain-to-grain (G2G) transfer technique and advanced inoculation methods, see Module 05 — Spawn Guide →

CO₂ is denser than air and accumulates at the bottom and interior of sealed fruiting chambers. Mushroom fruiting bodies are sensitive to CO₂ concentration during development — they naturally grow toward lower-CO₂ areas (toward openings and fresh air). When CO₂ is high throughout the chamber, the mushrooms elongate in every direction seeking fresher air, producing the "pins on stilts" appearance characteristic of poor FAE.

For most beginner setups: fan your fruiting chamber open or briefly fan air through it 2–4 times daily. A shotgun fruiting chamber (SGFC) with passive holes provides adequate FAE for small grows. Martha tent setups use a fan on a timer cycling on for 15–30 minutes every few hours.

Why Cold Shocking Works

In nature, shiitake and similar species fruit after autumn rains following summer heat — the combination of temperature drop and moisture signals the fungus that favorable fruiting conditions have arrived. The cold shock replicates this cue. For fully colonized shiitake blocks, the standard protocol is a 12–24 hour cold water soak in water at 55–60°F, then move to fruiting conditions. Pins typically appear within 5–7 days.

Cold Shock by Species

Identifying Trichoderma

• Color: Bright, vivid green — ranges from lime green to deep forest green depending on maturity. Not to be confused with blue or grey-green, which may indicate other mold species
• Texture: Initially white and fluffy like mushroom mycelium, then rapidly turns green as it sporulates (2–5 days)
• Timing: Most commonly appears in late colonization (60–90% colonized) when the substrate is nutrient-rich and the competitive landscape shifts
• Location: Often starts at injection ports, on grain that wasn't fully colonized, or on exposed substrate surfaces with poor gas exchange

Prevention — The Full Protocol

• Maintain sterilization protocols: Grain and supplemented substrates require full pressure sterilization; inadequately sterilized substrate is the most common Trichoderma entry point
• Keep incubation temperature at 70–78°F: Trichoderma's optimal growth temperature is 77–95°F — running incubation at or below 78°F suppresses its competitive advantage over mushroom mycelium
• Work in clean conditions during inoculation: Airborne Trichoderma spores are ubiquitous; even brief open-air exposure during inoculation can introduce contamination; use a still air box or flow hood
• Ensure adequate gas exchange: Stagnant humid air pockets create conditions where Trichoderma establishes; filter patches on grow bags and periodic airflow prevent this
• Inspect daily and act immediately: Green spots caught in the first 24–48 hours may be isolated; any green visible by day 3+ typically indicates systemic contamination

What to Do If You Find Trichoderma

Harvest Timing by Visual Cue

• Oyster mushrooms: Caps fully expanded, edges still slightly curled under (not flattened or wavy). Color at its most vivid. This is the peak flavor and texture window — 1–2 days past this, the mushrooms begin releasing spores
• Lion's mane: The white "teeth" are fully developed and dense but have not begun yellowing or browning. At first sign of any yellowing, harvest immediately — lion's mane turns bitter quickly after peak
• Shiitake: Cap has expanded to 70–80% of its full diameter, veil (thin membrane under cap) is beginning to separate from the stem but has not torn. Harvest before veil fully breaks to prevent spore release
• Button/Crimini: Harvest when caps are tight and rounded (closed veil stage) for button texture; allow more opening for crimini/portobello character. Avoid harvesting after the veil tears

Why Harvesting Before Spore Release Matters

Species with a partial veil (shiitake, button, many exotics) will tear the veil and release a spore cloud when the cap expands fully. For brown-spored species, this creates a fine brown/purple powder coating every surface in your grow space — difficult to clean, can cause respiratory irritation with repeated exposure, and marks every subsequent surface it lands on. Harvest 24–48 hours before you expect veil break to avoid this entirely.

Harvesting Technique

• 1Harvest entire clusters: For oyster mushrooms, grip the entire cluster at its base and twist gently while pulling outward — the cluster detaches cleanly. Do not harvest individual caps from a cluster; this leaves stems that rot and invite bacterial contamination.
• 2Or cut at the base with clean scissors: Some cultivators prefer cutting to avoid disturbing the substrate. Wipe scissors with 70% isopropyl between flushes.
• 3Remove all stub material: Any stem stubs left in the substrate after harvest will rot. Remove or scrape clean after each flush.
• 4Rest the block: After harvesting, allow the block to rest in lower humidity for 3–5 days (rehydrating if dry) before returning to full fruiting conditions. Most species produce 2–4 flushes from a single block before yields diminish.

Fresh Storage

• Paper bag in the refrigerator: The industry standard — paper allows gas exchange and prevents moisture buildup. Avoid plastic bags (condensation leads to rapid sliminess) and airtight glass (CO₂ accumulates)
• Temperature: 32–40°F (0–4°C); avoid the coldest zones of the refrigerator where freezing can occur
• Do not wash before storing: Surface moisture dramatically accelerates spoilage; brush dirt away dry and wash only immediately before cooking
• Shelf life: 3–7 days at refrigerator temperature in a paper bag; oysters and lion's mane on the shorter end; shiitake more robust

Dehydrating for Long-Term Preservation

• Dehydrate at 95–115°F in a food dehydrator until mushrooms are completely dry and brittle — no pliability remaining (typically 4–8 hours depending on mushroom thickness and water content)
• Target moisture content below 10%: Mushrooms that feel slightly flexible still contain too much moisture and will spoil in storage; err on the side of over-drying
• Vacuum-sealed in a mason jar or food-safe bag: 2–5 years at room temperature in a cool dark location. Loosely stored in a jar with air exposure: approximately 1 year before noticeable flavor loss
• Rehydrate before cooking: Soak in warm water for 20–30 minutes, or add directly to soups, stews, and sauces — rehydrates as it cooks