Mossy — King Blue OysterGrain Spawn 5 lb

King Blue Oyster Mushroom Spawn – 5 lb Bag

King Blue Oyster (Pleurotus ostreatus hybrid) was the first cross created by Andrew Reed of Mossy Creek Mushrooms in Tennessee — a blue oyster crossed with a white elm oyster, pairing blue colouring with the elm oyster's large, thick stems. The result is a robust strain that fruits in large, heavy clusters with meaty fruit bodies that appeal to chefs and consumers who want more substance in their mushrooms. It is an excellent choice for Canadian growers looking for a high-yielding, dependable strain that produces premium-quality mushrooms year-round.

Why Growers Choose King Blue Oyster

• Large, heavy clusters – Produces bigger individual fruit bodies with thick stems, increasing the weight per harvest.
• Little trim waste – Nearly uniform texture from cap to stem means almost the whole cluster is saleable.
• Substantial texture – Thicker stems and meatier caps compared to standard Blue Oyster, with a deep savoury flavour.
• Strong colonization – Vigorous mycelial growth reduces contamination risk and keeps your production schedule on track.

What You Get

Each 5 lb bag contains fully colonized organic millet grain spawn from our CFIA-licensed production facility in Brantford, Ontario. Every batch is produced in-house from lab-isolated genetics under strict sterile conditions. This ensures you receive consistent, contaminant-free spawn that performs reliably at scale.

How to Use

Mix grain spawn into pasteurized straw or supplemented hardwood sawdust at a 10–15% spawn rate. King Blue Oyster is versatile and does well on both substrates. Pack into XL grow bags or growing columns and colonize at 20–24°C. Once colonized, move to fruiting conditions with high humidity and fresh air. Expect dense, blue-grey clusters that mature over 5–7 days.

Growing Conditions

• Fruiting temperature: 13–24°C (55–75°F); tolerates a wide range but keep rooms below 29°C
• Humidity: 85–95% RH during fruiting
• Light: Indirect ambient or 12-hour cycle
• Fresh air: High air exchange for compact, well-formed clusters
• Substrates: Pasteurized straw, hardwood sawdust, masters mix

Looking for a classic king-style stem? Try our Black Pearl King Oyster Mushroom Spawn. Need growing supplies? Browse our grow bags and substrate options.