Grain spawn is sterilized grain pre-colonized with live mushroom mycelium. We start with pressure-sterilized organic sorghum, inoculate with a verified strain of the species you want to grow, and incubate until mycelium has fully colonized the grain. The result is a bag ready to "spawn" the next stage of your grow — mix it into bulk substrate and the mycelium expands across the substrate to fruit mushrooms. Saves you the inoculation and colonization phases entirely.

Open the bag in a clean environment. Mix the colonized grain directly into a bulk substrate bag at roughly 1:2 to 1:3 spawn:substrate ratio — work the spawn through evenly. From there you have two paths: heat seal the bag closed for grow-in-bag culture (slit and fruit once colonized), or empty into a monotub for higher-humidity bulk fruiting. Incubate at approximately 76°F until pin sets appear, then move to fruiting conditions.

Grain spawn is already colonized with a specific species — ready to mix into bulk substrate. Saves time and removes one inoculation step from your workflow. Grain media is sterilized but uninoculated grain — you inject with liquid culture and grow your own spawn. Media is more economical per pound and gives you full species control; spawn saves 2–3 weeks of colonization time and removes one chance for contamination. Most experienced cultivators use both, depending on the run.

Fresh grain spawn is best used within 2–4 weeks of receipt, refrigerated until use. Mycelium continues to consume the grain's nutrients over time; spawn that sits too long loses vigor and starts to favor sectoring or rhizomorphic deterioration. Refrigerate immediately upon arrival, and time your bulk-substrate prep so you can mix the spawn in within a couple of weeks of getting it.

Spawn is produced in small lab-verified batches rather than continuous bulk runs — this keeps strains fresh and verified but means individual species cycle in and out of stock. The fastest way to be notified when a specific species is available again is to click into that product page and use the back-in-stock signup. We restock most species on a rolling basis.