I am growing mushrooms indoors on coffee waste, and I am trying to find a DIY system to water them automatically.

Basically, the reasons why it is different than watering plants are: - You don't know where the mushrooms are going to pop out on the substrate surface, so the whole area has to be (more or less) uniformly wet all the time. - They are very sensitive, especially in the early phase. If they are dry for a few hours, they'll stop growing and die.

It could be a system involving a small tank that I need to fill every other day or something like this. I am just looking for a way to avoid having to spray them twice daily or more like now.

So you have an idea of the size, I am currently using wooden wine boxes. However, I might get/build something larger, so the new box can probably be adapted to the watering system if it needs to be.

My first idea was a kind of clothe that I would spread out on sticks over the mushrooms. I guess some clothe could be tight enough so that the water takes time to percolate through and drop on the mushrooms...

Any other ideas?

3 Answers 3


I like the mister idea as long as you have humidity sensors as well as have been maintaining and watering your own mushrooms with your own hands manually. It is a delicate balance for moisture and medium especially for mushrooms. To put your shrooms on a schedule you should see a pattern as you manually get to know the needs of your crop, no one else could set a timer for you.

A simple gravity fed medium using a network of tiny hoses with holes from a higher water source seemed to work for a friend of mine but he had to cut the water off manually when at proper moisture/air levels.

Another way to grow plants is to moisten the medium and cover the entire kaboodle with a plastic cover to hold the moisture a long time. Like a terrarium. Gotta know the proper humidity levels and how important it is to keep enough air in the medium and air movement around the mushrooms. Worth looking into especially to get the plant producing 'sexual organs' as the real plant is beneath the soil. Yes? So there are two environments necessary to monitor; the one the plant (fungus mycelium) is embedded in and the crop or fruiting bodies sexual organs in the air.

Have you been doing this for awhile? The pure coffee grounds as medium bothered me so I went out to find this following article about coffee grounds. I am not liking PURE coffee grounds for your medium. It should be only a smallish part of the medium, the rest being sawdust or straw...

I am not a mushroom growing officianado but this sounds sort of a fad that has gone overboard. Similar to 'low carb diets'...our desire for numbers, novelty and magic without basic criteria with which to be able to think through these newbie methods causes failure and much grief. Is there something in nature you can compare this method with? If not, I would be instantly suspicious. Coffee grounds are uniform, yummy texture, yummier color and smells yummiest. But sometimes a little is a good thing and more is not so great.

Read this link I am sending. mushrooms and coffee ground medium Please let me know what you think.

  • I've done only one batch until now so I'm really an early beginner, but it worked beautifully (with oyster mushrooms). Article is interesting but I do not agree much, maybe they're talking about particular kits or harder-to-grow mushrooms. I did not used kits, I think they are cool, but probably a bit of a rip-off. I only bought spawn online, asked coffee grounds in cafés around, and used this guide (growveg.com/guides/…). Commented Nov 22, 2016 at 8:37
  • So I've used pure coffee grounds. True, I cannot compare with anything in nature, but I'm not sure that's a good point. Pretty much any growing you do is very far from natural conditions anyway. And the beauty of the coffee waste method is not about the molecules it contains, but because it was already boiled, so it is sterile (enough), and your mycelium doesn't have to compete with other molds. I think the mushrooms are going to use pretty much only the cellulose in your substrate. Anyway, I'll be happy to try other substrates, maybe they give even better results. Commented Nov 22, 2016 at 8:47
  • And thanks for your watering ideas, they look very interesting. I feel like the mushrooms, once they are big, need to be watered from above to stay humid and continue to grow (I don't think the mushrooms have a circulatory system to pull the water from the substrate to the top cells like plants), so I'm not sure the gravity fed medium would work during the final phase. But I might be wrong. Commented Nov 22, 2016 at 8:52
  • Hey, mushrooms push the boundaries of the plant world. I'm hugely fascinated with this fungus/plant. Sounds like you've got solid foundations for this stuff. It is tough to be a devil's advocate but I like that you were able to support your process. I don't think mushrooms need to be watered from above, though. Remember they are literally sexual organs of the fungus...the main body beneath the soil. What kind of water are you using? If you are using city tap water, you should look into what is in that water. I'd get well water or purchase distilled or bottled water.
    – stormy
    Commented Nov 22, 2016 at 10:12
  • They are actually closer to animals than plants, which I find really fascinating too (I mean, this white fluffy thing is closer to a human than to a fern... Crazy)! You may be right, I am going to try watering from below, it could work (especially if I find a way to seal more or less hermetically the whole stuff, the environment inside should stay humid). Yes, I am using city tap water. Right, I did not think about this variable before. I know my tap water is very hard, do you have any idea if that's good/bad/without effects to the mushrooms? Commented Nov 22, 2016 at 11:17

The easiest answer is to buy a mister like for dart from and set it on a timer. You'd simply keep the reservoir filled and set the timer to come on multiple times a day to keep whatever consistency of moisture you want.

  • Thanks Dalton. Are you saying a Mister humidifier? Not sure I fully understood the sentence sorry. The box would be open though, and I cannot easily put the humidifier inside it. Do you think that if I just put the humidifier next to the open box that would be enough to wet the mushrooms? And what about a more DIY system? Any idea? Commented Nov 21, 2016 at 19:51
  • An ultrasonic humidifier freshcapmushrooms.com/learn/… Commented Jan 2, 2018 at 22:20
  • @francoiskroll Looks like I did some misspelling there. Graham's answer could work fine, but I was talking about something like this: amazon.com/Zoo-Med-Reptile-Terrarium-Humidifier/dp/B0019IJXD2
    – Dalton
    Commented Jan 4, 2018 at 20:53

It is important to provide moisture to the air - not only the substrate.

One option is, as @stormy proposes, a mist(fog) machine. One options is a piezo one but there are others. Pay attention to get one without LEDs else the mushrooms will curve towards it. enter image description here

A lazier and cheaper option is to grow the mushrooms on a raised bed above moist perlite(get it from any hardware/building materials shop for a dime). The large surface area ensures increased evaporation compared to simple water container.

Of course both options assume enclosed volume, vented a couple of times per day, proper temperature control and some minimal light coming strictly from above.

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