I recently started a brown oyster mushroom grow kit. It came with a plastic sleeve for keeping moisture in until pinheads form. After a large mushroom emerged, I removed the sleeve. This morning, I noticed that splits have appeared on top of the mushroom:

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Are these splits benign, or do they indicate that the mushroom has too little moisture? If this is an indication of dehydration, what is the best way to fix it?

1 Answer 1


The mushroom is totally healthy, but you are right, it's due to dehydration. Actually it's common case for many mushroom species

Mushroom block may be moist enough, but the air outside is too dry.

Mushrooms consist 90% of water and require relative humidity (RH) about ~90% for pinning and fruit bodies development as well, when room RH vary from 30% to 70%.

So it's sharp difference! As a result, mushrooms lose moisture extremely fast. That's why these splits appeared.

To maintain high RH (for home growing) cultivators use simple fruiting chambers - plastic tub 40-80Qt with manual misting (aerosol misting bottles are great to use) or terrarium humidifier + fresh air exchange with air pump, fan, or manual fanning (mushrooms breath and also need oxygen)

Or grow tent with manual misting (aerosol misting bottles) or terrarium humidifier/fogger

To check RH just use simple hygrometer

Have a happy growing!

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