How to Grow Grey Oyster Mushrooms
Full Cultivation Guide

Phase 1: Preparation & Induction

Grey Oyster mushrooms grow best in clusters.
Unlike Eryngii (top fruiting), Oysters are often induced through specific openings to mimic growing from the side of a tree.

• Placement
  Position blocks on shelves. Ensure there is enough vertical space between shelves (approx 40-50cm) as Oyster clusters can grow quite large.
• The “Cross-Cut” Technique
  Do not remove the bag entirely. Instead, use a sharp, sterile blade to cut X-shaped slits (approx 5cm wide) into the plastic.
  – Option A (Side Fruiting): Make 2-4 slits on the sides of the bag.
  – Option B (Top Fruiting): Cut the top of the bag off completely (only if humidity control is perfect), OR make slits on the top surface.

Why Slits? The plastic retains moisture within the block while the opening directs the mycelium to form a tight, energy-dense cluster at the exit point.

Phase 2: Primordia Formation (Pinning)

Once fresh air hits the substrate through the slits, pinning begins rapidly (usually within 3-7 days).

• Humidity
  Keep RH at 90%. The exposed substrate at the slit must not dry out.
• Temperature
  A slight temperature drop (Shock) to 12-13°C can help trigger a synchronized pin set, though our strains are vigorous enough to pin at steady temperatures.

Phase 3: Fruitbody Development

This is the phase where shape is determined.

• The “Fresh Air” Rule
  Grey Oysters are the “canaries” of the mushroom world.
  If CO₂ levels rise above 900 ppm, the mushrooms will stretch, developing long, thin stems and tiny caps (antler/coral shape).
  Ensure constant air exchange.
• Lighting
  Maintain 1000-1500 Lux (bright enough to read a newspaper).
  Insufficient light results in pale, weak clusters.
• Watering
  Mist the environment, not the mushrooms.
  Wet mushrooms are prone to bacterial soft rot.

Phase 4: Harvest

Harvest timing is fast—Oysters can double in size every 24 hours.

• When to Harvest
  Harvest when the cluster is large and the cap margins are still slightly curled down or just flattening out.
  Do not wait for the caps to crack or curl upwards completely, as they will release massive amounts of spores.
• Technique
  Harvest the entire cluster at once. Twist the base of the cluster and pull cleanly.
• Cleaning
  Remove any residual stem tissue from the slit to prepare for the next flush.

Important — Worker Safety (Spore Load)
Pleurotus ostreatus is a heavy spore producer, particularly for strains used on straw-based substrates.
When mature, they release clouds of spores which can cause respiratory irritation (“Mushroom Worker’s Lung”) over time.

The strains we use for our wood-based oyster are sporeless strains.
It is more common for grey oyster varieties on straw-based substrates that contain spores.

Recommendation
When working with straw-based substrates, we strongly advise staff to wear P2/P3 respiratory masks during harvesting.

Early Harvest
Harvesting before the caps fully flatten significantly reduces spore load in the growing room.

Disclaimer
These instructions are general guidelines for CNC substrates. 
Optimal parameters may drastically vary depending on your specific growing facility design and environment.