What Are Mushroom Grow Bags?
Mushroom grow bags are self-contained, sterile growing environments designed to make cultivating mushrooms at home simple and reliable. Each bag contains a substrate — typically a mix of straw, sawdust, or grain — that has been sterilised and inoculated with mushroom spawn. All you need to do is provide the right conditions and wait for nature to do the rest.
At MUSHROOMTEC, our Mushroom Grow Bags with 0.2 Micron Filter Patch are made from 3.2 mil thick, autoclavable polypropylene — built for serious home growers and professionals alike.
Step 1 — Choose Your Mushroom Variety
The most popular varieties for beginners in the UK are:
- Oyster Mushrooms (Pleurotus ostreatus) — fast fruiting, forgiving, and prolific. Ideal for first-time growers.
- King Oyster (Pleurotus eryngii) — slower but produces thick, meaty stems with excellent shelf life.
- Lion's Mane (Hericium erinaceus) — unique appearance, high demand, and great for more experienced growers.
Step 2 — Set Up Your Growing Environment
Before opening your grow bag, you need a clean, controlled space. Contamination is the number one reason beginner grows fail.
- Temperature: Most oyster varieties fruit best between 18–24°C.
- Humidity: Aim for 85–95% relative humidity during fruiting. Mist the bag opening 2–3 times daily.
- Fresh Air Exchange: Mushrooms need CO₂ to escape. Fan the opening briefly when misting.
- Light: Indirect light for 12 hours per day helps trigger pinning. Direct sunlight is not needed.
Our XXL MushroomTec Still Air Box Monotub Kit includes a built-in temperature and humidity gauge — perfect for monitoring your grow without guesswork.
Step 3 — Inoculate or Use Pre-Inoculated Bags
If your bag is already inoculated with spawn, skip straight to the colonisation phase. If you're starting from scratch:
- Work inside a still air box or flow hood to minimise contamination risk.
- Inject liquid culture or add grain spawn through the self-healing injection port or filter patch.
- Seal the bag and store in a warm, dark location (20–25°C) for colonisation.
Step 4 — Colonisation Phase (1–3 Weeks)
During colonisation, white mycelium will spread through the substrate. This is normal and healthy. A fully colonised bag will be almost entirely white throughout. Do not open the bag during this phase.
Watch out for: Green, black, or pink patches — these indicate contamination. Remove the bag from your growing area immediately if you spot these.
Step 5 — Initiate Fruiting
Once fully colonised, it's time to trigger fruiting:
- Cut a 5–10cm X or cross shape into the side of the bag where you want mushrooms to emerge.
- Introduce a cold shock if needed — move the bag to a cooler area (15–18°C) for 12–24 hours.
- Begin misting the cut area 2–3 times daily and ensure good airflow.
- Pins (tiny mushroom primordia) should appear within 5–10 days.
Step 6 — Harvest
Harvest your mushrooms just before the caps fully flatten and the edges begin to curl upward. Twist and pull gently at the base — do not cut, as this can leave stumps that rot and cause contamination.
After your first harvest (flush), mist the bag, allow it to rest for 5–7 days, and a second flush will typically follow. Most bags will produce 2–4 flushes before the substrate is exhausted.
Ready to Start Growing?
Browse our full range of mushroom cultivation equipment at MUSHROOMTEC — from autoclavable grow bags to complete Inflatable Monotub Kits and our XXL Still Air Box Kits with integrated environmental monitoring.
Happy growing! 🍄