Preparing Your Mushroom Grow Room for Winter

When the cold weather rolls in, mushroom growers face a new challenge — maintaining the perfect environment for healthy, consistent fruiting. Temperature swings, low humidity, and dry indoor air can all impact your yields if you’re not ready for them. The good news? With a few simple adjustments, you can keep your grow thriving all winter long.

Here’s your complete guide to winter-proofing your mushroom grow room.

1. Maintain Stable Temperatures

Most mushroom species prefer a steady range between 70–80°F during colonization and 60–70°F during fruiting. In winter, indoor temps can fluctuate more than usual, which can slow colonization or even stall growth.

Tips:

• Use a digital thermometer or hygrometer (like the ones sold at Colorado Cultures) to monitor conditions.

• Add a small space heater with a built-in thermostat to maintain a consistent temperature. Avoid pointing heat directly at your grow bags or tubs.

• If using a grow tent, insulate the walls with reflective mylar or foam board to retain warmth.

2. Combat Dry Winter Air

Cold air holds less moisture, and indoor heating systems make it even worse — dropping humidity levels below what mushrooms love (usually 85–95% for fruiting).

Tips:

• Run a humidifier or misting system to keep your fruiting chamber hydrated.

• Mist lightly but frequently if humidity dips below target levels.

• Use plastic sheeting or zippered tents to trap humidity around your fruiting area.

  
  

3. Improve Airflow Without Losing Heat

Fresh air exchange (FAE) is critical for strong, healthy mushrooms — but cold drafts can quickly drop your temperatures.

Tips:

• Use small oscillating fans on low settings rather than open vents or windows.

• Add inline fans with filters if you need more airflow without temperature loss.

• Run fans on timers to balance oxygen levels while keeping warmth stable.

4. Adjust Your Light Schedule

Mushrooms don’t rely on intense light but do respond well to consistent exposure.During darker winter months, supplement with LED grow lights or daylight-spectrum bulbs on a 12-hour light cycle.This ensures even growth and helps your mushrooms orient properly during fruiting.

5. Keep It Clean and Contamination-Free

Cold months often mean more time indoors — and more potential for contaminants to spread. Dust, mold spores, and bacteria thrive in enclosed spaces.

Tips:

• Wipe down surfaces with isopropyl alcohol regularly.

• Keep HEPA filters or air purifiers running if possible.

• Store unused substrates and supplies in airtight bins.

• Use Denver Dirt substrate or other high-quality sterile materials to reduce contamination risk.

6. Bonus: Optimize with Fungi Fuel

Winter can slow biological processes — including mycelium growth. A boost of nutrients like Fungi Fuel can help your culture stay vigorous even when the temperature dips. Simply add it to your substrate or grain bag to give your mushrooms an extra energy source during the colder months.

Final Thoughts

Winter doesn’t have to slow down your grow — it just means adapting your setup to match the season. With stable temps, high humidity, and a clean, controlled environment, you can keep producing healthy flushes all year long.

If you need help optimizing your setup, stop by Colorado Cultures’ Lakewood or Englewood locations to talk to our team, or shop online for grow bags, substrates, and cultivation tools designed to keep your mushrooms happy all winter long.