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June 8, 2022

Maintaining High Humidity: Mushroom growing tips

New to mushroom growing? Here's an in-depth guide to help you create the humidity that they require.

High humidity is required, but only during the 5 days that the mushrooms are actually growing. The rest of the time they will have access to plenty of moisture from within the bag.

During this stage optimally humidity will be about 80-90%

Our rule of thumb: if you think the mushroom growing location would be a good place to dry damp clothing. That would be a bad spot!

A. Locations for growing mushrooms

Growing Oyster mushrooms is best done indoors. Here's a rundown of the best locations in your house.

See our more in-depth article about the best locations to grow mushrooms

Problem areas

Best locations

  1. Inside the shower cubicle
  2. Bathrooms

Inside the shower stall will be the most humid area in your house, and a good spot to put it while you are learning the ropes. Just put it on a plastic stool after you have had a shower. Bathrooms are also good, especially in winter. Close the door if you are operating heatpumps.

Okay locations

  1. Kitchen
  2. A shed or garage (with care)
  3. Glass or greenhouse

Many people have done well, growing mushrooms in the kitchen. Keep a close eye on them, if it's struggling then move them to the shower/bathroom. Garage, sheds and greenhouses are generally okay, as long as they are a little damp and not too hot over summer. Also, keep an eye out for pests.

  1. Open Living spaces that use heat pump/air-conditioning or other drying heat

Bad locations.

  1. Draughty locations (usually dry air)
  2. Enclosed spaces (cupboards etc)
  3. Outside in an unenclosed location

Worst location

  1. Hot water cupboard
  2. Under a house
  3. bedrooms

B. Tools that can help.

1. Humidity sensor.

If you have one of these, you can check the natural humidity in different areas of the house to identify a good location. You will have a couple of weeks before the mushrooms start growing to work out where to put them.

 

pond fogger
A pond mister/fogger

A fogger from Gardens Alive (NZ)

2. Pond Misters

These are the best solution for raising humidity but requires preparation to use them properly. Generally, you will need to do this in a container to trap the humidity or it will quickly dissipate.

An alternative to this could be to use misters used for aroma therapy or room humidifiers.

3. Perlite

This can work well, particularly during warmer months as it required natural evaporation of water to raise humidity. It will also need to be done in a container like a large plastic tub. The tub will need to have air holes created and possibly a small USB fan (on a timer) to create airflow.

Pour it into the bottom of the container till about 7cm covers the bottom. Then pour in a litre or two of water. The idea is that it’s not fully submerged. The perlite is porus and has the effect of massively increasing the surface area of the water, aiding in rapid evaporation.

4. Fans for airflow.

If you have it located in an enclosed space, a cheap USB fan should move enough air to keep it fresh (as long as its pulling ‘in’ fresh air. We recommend having this on a timer set to 15min every hour. Again this is only required for the 5 days that the mushrooms are growing.

a note on airflow

The growing mushrooms will need plenty of fresh air. If they are in an enclosed location they will quickly build up carbon dioxide, through their respiration, much like we would. This will cause the mushrooms to deform, often growing long stems and small caps.

5. Misting Bottle

This is the simplest method as it does not require any additional equipment or building a container. However, it works best only in situations where you already have a fairly high level of natural humidity. So, it should work if you have it in a bathroom, or possibly a kitchen. The frequency of misting will depend on the location, so may require some trial and error to get right. If it is in a bad location the misting method will not be enough.

misting bottle mushroom humidity
Good ol' misting bottle
jade plant mushroom companion for humidity
Jade Plant
Spider plant mushroom companion planting
Spider Plant

6. Companion planting

If you have green thumbs and enjoy growing indoor plants, you can arrange them in a way that they will add to the humidity and oxygen available to the mushrooms.

Although technical here’s some information about how Spider and Jade Plants can Improve relative humidity inside the home. https://krex.k-state.edu/dspace/bitstream/handle/2097/35195/803.full.pdf

For the same reason, an active glasshouse can also work well. However, see our tips on mushroom pests.

Plants from Bunnings garden centre.

Spider plant

Jade plant

7. Mushroom growing containers

Large plastic containers are great at raising humidity and keeping it in, but they will need to be ventilated as they will not allow enough air exchange. This will lead to deformed mushrooms. When using a container you will need to balance the humidity, with fresh air without drying the mushrooms. For instance, a fan blowing directly onto the mushroom will dry it quickly.

See our article about building a humidi-crib

An alternative would be to use a small photographic ‘light’ tent or soft box . This has the added benefit of making it easier to photograph while it is growing.

Light tent from Auckland Camera

mushroom growing container
Plain old plastic tub
light tent mushroom grow container
Light Tent

C. The weather and growing mushrooms

Levels of humidity, within your home, will fluctuate depending on the time of year.

Summer

Good, especially if there has been raining or you live next to the ocean or have plenty of bush/forest nearby.

Autumn

Perfect. Early autumn is the best time for mushroom growth as the weather is generally warm with high rainfall.

Winter

Care required: Winter can be difficult. This is because we often have heating and ventilation systems within the home to keep it dry, and to stop other pesky fungi like moulds from growing. Much of the humidity in the air will also condense on windows. Extra care needs to be taken. Note: Throughout most of NZ lack of humidity is the problem, not the temperature.

See our article about growing mushrooms in winter

Spring

Good: Like autumn this can be a good time of year as natural humidity will be raising and with windows open, some of the humidity outside is allowed in. However, depending on where you live.

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