Guerrilla — Black OysterGrain Spawn 5 lb

Black Oyster Mushroom Spawn – 5 lb Bag

If you are looking for a proven workhorse species to anchor your mushroom operation, Black Oyster (Pleurotus ostreatus) is hard to beat. Known for aggressive colonization, reliable flushes, and impressive biological efficiency, this strain is the go-to grain spawn for farms across Canada. Whether you are scaling a commercial grow room or running a market-garden side hustle, Black Oyster delivers consistent results with minimal fuss.

Why Growers Choose Black Oyster

• Fast turnaround – From inoculation to first harvest in as little as two to three weeks on straw, making it ideal for rapid production cycles.
• Versatile substrate range – Thrives on pasteurized straw, supplemented hardwood sawdust, and masters mix, so you can work with whatever feedstock is available in your region.
• High yield potential – Multiple productive flushes mean more pounds per bag and better margins for commercial growers.
• Beginner-friendly – Forgiving genetics that tolerate a range of growing conditions, making it an excellent first species for new cultivators.

What You Get

Each 5 lb bag contains fully colonized organic millet grain spawn produced in our sterile, CFIA-licensed production facility in Brantford, Ontario. Every batch is made from lab-tested genetics to ensure vigour, purity, and performance. We produce all of our grain spawn in-house so quality is never left to chance.

How to Use

Break up the grain spawn and mix it into your prepared substrate at a rate of roughly 10–15% by weight. For straw-based grows, pasteurize your straw, drain thoroughly, and layer or mix in the spawn before packing into grow bags or containers. For supplemented sawdust blocks, mix the spawn evenly during bag filling and seal for colonization. Maintain colonization temperatures around 21–24°C with good air exchange.

Growing Conditions

• Fruiting temperature: 15–21°C (59–70°F)
• Humidity: 85–95% RH during fruiting
• Light: Indirect ambient light or 12-hour lighting cycle
• Fresh air: Good air exchange to promote healthy cap development
• Substrates: Pasteurized straw, supplemented hardwood sawdust, masters mix

Looking to try other oyster varieties? Check out our Blue Oyster Mushroom Spawn for a cold-tolerant alternative, or explore our full lineup of mushroom spawn available across Canada.