Is a constant high rH enough to keep mushrooms fully hydrated without added water?

So i set up this “fruiting chamber/tent” today, equipped with a humidifier, hygrometer and fan.
(Picture below)

A question came to mind, lets say for example i kept humidity at 90% - an ideal rH for a certain mushroom species which is in its fruiting process. Would they still require water from a spray bottle or is the constant 90% humidity enough to keep them well hydrated?

P.S. I am considering adding a tube of ventilation if the fan isn’t adequate for FAE requirements

1 Like

Nope, that level of humidity will be enough to ensure that the substrate doesn’t dry out; no spraying required. The substrate will naturally lose water as mushrooms are produced and harvested.

Bear in mind that the rate of dehydration of the substrate also depends on how much surface area is exposed. If you took your oyster grow-kit and removed the box and all the plastic, so that the entire block of substrate was exposed, that would lose moisture quicker than if you kept it wrapped-up with just a cut or two in the plastic.

If you’re interested, I can offer a few pointers for running this kind of setup. I don’t want to dump unwanted info on you :laughing:

Awesome! Yeah please share if you willing, id be interested to hear about it actually.

And quite impressed u figured out just from the picture that was an oyster grow kit!

Right on. Here you go (I’ve run a similar tent for a couple of years):

Move the humidifier outside of the tent and pipe the humidified air in. This will drastically increase the lifespan of your humidifier (there are electrical components inside which will corrode and fail very quickly in high humidity). It’ll also make it easier to refill the reservoir without having to open the tent. You’ll have to improvise the piping; I’ve used swimming pool pipe to good effect (you want something that’s flexible and easy to clean).

You’ll need to reinforce a section of the plastic tent where the pipe enters; you can do this by creating a rectangle with a few layers of duct tape (the idea is to prevent the plastic from tearing). I like to place this entry point on the side, at roughly the level of the first shelf (you could also place it on one of the slanted ‘roof’ sections). The humidified air will fall downward as it leaves the pipe.

Depending on the species you’re growing, you will very-likely need more airflow. With oysters (Pleurotus spp.) you can probably get away with simply leaving both door-zippers unzipped and running an oscillating fan in your room. A species like Hericium erinaceus prefers more fresh-air exchange (FAE) so you will either have to pipe fresh air in or modify your tent. I got excellent results by making a grid of small holes over the entire surface of the plastic cover. The downside to that approach is having to melt plastic…not fun (if you do this, do it outside).

Um…what else…watch out for mold growth on the inside of the tent. You’ll need to clean at least once a week when it’s in full-swing. If you ever start seeing weird growth in your mushrooms, it’s probably the result of a contaminant that you’re not seeing.

Be aware that the shelves are going to rust. There’s no real way I know of to prevent this. This is why stainless steel is ultimately the way to go. That being said, the tent you have will serve its purpose for the time being. You can always level-up to a cannabis-style grow tent and stainless steel shelves at a later time.

You might already be doing this but it can be helpful to run the humidifier on an timer. That will give you a lot of control in order to dial-in your setup. For example, you might find that running the humidifier at 1/4 “power” for 15 minutes every hour is just-right.

I hope that’s of some use!

1 Like

Ok great, so ill be going to the shop to get the materials necessary to make these modifications.

I think my biggest problem/concern is lowering the inside air temperature, havent thought of a full proof solution yet thats cost effective…currently its very hot and humid in Cape Town and not ideal fruiting conditions

That actually makes sense about the humidifier life span and the mold (definitely will clean out the tent once a week)

Im actually testing using some antibacterial essential oils in the humidifier to try minimize mold buildup (keeping in mind not to use a fungicide) - have no clue if this will work but its fun and smells nice at least. (Currently using Rosemary and intend to try cinnamon)

this is cool to see… I tried a similar setup last spring with oysters… I was less prepared, didn’t use a fan, and they never fruited. later in the kiezpilz fruiting chamber with more FAE the same strain fruited. So I suspect lack of air exchange was my problem

its funny imagining so many people having this same shape green house full of mushrooms…

1 Like

One low-tech, low-input approach is to engage in seasonal production: grow heat-loving species in the summer and cold-tolerant species in the winter. If you are focused on Pleurotus spp. production for food then you could run Pleurotus djamor (‘pink oyster’) and / or Pleurotus pulmonarius (‘phoenix oyster’) in summer, Pleurotus ostreatus (‘pearl oyster’) in the winter and Pleurotus citrinopileatus (‘golden oyster’) in the spring and autumn.

A simpler approach, since you’re just getting started, would be to run two species: one in autumn-winter and another in spring-summer.

The seasonal approach is the way to go, in my opinion, and far superior to using energy-intensive and expensive climate-control measures.

This sounds like a super interesting line of research / inquiry! I’m excited to hear how it works out for you.

1 Like

Thanks guys

@notplants , I could imagine so many people having this set up and makes me chuckle a bit too. Basically the entry point fruiting chamber.

Ill keep u posted Glyph with regards to the essential oils. Went to the hardware store today to check out some ventilation piping and extractor fans. When cash flow permits ill be making the necessary modification. (Right now my spore load is low so not absolutely essential this moment)

And what u said about the seasonal mushrooms makes a lot of sense. Just excited to have species like Reishi and Lions mane on a all year round basis i gues.

Bit of a paradox since i firmly advocate the use of eating foods that are in season. But i really like that and definitely going to plan around seasonal mushroom growing.

Love the sheer versatility and application of the Pleurotus genus. Highly underestimated fungi, that could have multiple threads on this network im sure. (The plastic eating potential is something i want to explore at some point)

Anyways there i go again trailing off topic!
Thanks again :slight_smile:

Ganoderma lucidum thrives in hot temperatures - it is an ideal candidate for summer growth in Cape Town. In my experience, Hericium erinaceus is surprisingly tolerant of warm temperatures - though I wouldn’t push it too far past 26°C. The fortunate thing about summer in Cape Town is that it generally cools down quite a lot at night.

It’s also worthwhile to remember that genetics can make a big difference when it comes to temperature tolerance; many species can be found in cold-tolerant and warm-tolerant strains. Here’s a paper which deals specifically with fruiting tolerance of Hericium spp.:

Atila, F., Tüzel, Y., Pekşen, A., Cano, A. F., & Fernández, J. A. (2021). The effect of different fruiting temperatures on the yield and nutritional parameters of some wild and hybrid Hericium isolates. Scientia Horticulturae, 280, 109915.


  • Hericium spp. and even the strains belonging to H. erinaceus need different temperatures for fruiting.
  • Increasing temperatures led to decreased protein and ash content of fruitbodies.
  • Other nutritional contents of strains were not affected by the fruiting temperatures.
1 Like