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There can be too much of a good thing. Mushrooms can be very beneficial for plants they cohabitate with, and they are definitely good for them once they are turned into compost. However, a compost mix that has too many mushrooms can create too many problems.

Mushroom compost can stay too soggy, rendering it unusable or even turning it into the perfect breeding ground for mold and other undesirable. And the same way that all the medicine is poison but just in smaller doses, compost with a high mushroom content can even damage or kill your plants if you use it too much and too often.

Why are mushrooms good for composting?

They work in two ways to make your compost better. First, they are decomposers, which means that they will speed up the composting process. That will also help release additional nutrients that may be hiding somewhere in the composting material.

Second, they themselves are nutrition powerhouses. They are very rich in nitrogen which your plants love. They are also full of numerous minerals that will keep the soil healthy and happy.

It doesn’t take a lot of mushrooms to get these benefits either. Basically, whatever it is that your kids (or whoever is the pickiest eater in your home) leave on their plate after dinner will get you an extra step to these benefits.

And if that’s all that you’re adding to your compost (mostly casual meal leftovers), you can pretty much just add them to the mixture as you would add any other kitchen scraps. But if you plan on using more than that, you will have to pay more attention.

What is mushroom compost not good for?

Growing fruits. Technically, most of the botanical fruits (that means tomatoes too).

Pretty much, if there is an elevated level of acidity in produce, you should skip the mushrooms. They themself prefer materials that are more pH neutral.

What are the signs that I have too much mushroom in the compost?

The compost itself will be very soggy. It will not be able to achieve that crumbly, wet soil consistency you are looking for. It can also start smelling more moldy than earthy. The last part is also a sign that the fact that the compost is wet enough to start developing other issues.

But if you’ve already used the compost, you will see your plants grow and get green and rich very quickly. But then, the situation will turn quickly and your plants will slowly wither and lose their plumage. Adding more mushroom compost in an effort to revive them will be counterproductive.

What will happen to plants if I use compost with too many mushrooms?

They may start growing mushrooms. Though this is mostly the case if there are some spores that managed to survive and (by some miracle) didn’t start growing into shrooms while your compost was “cooking”.

But, as mentioned, you will probably have to deal with the excess of nitrogen. Nitrogen will boost foliage growth and you will end up with some lush greenery, but that will come at the cost to the roots and fruits of the plant. Good if you’re trying to get some privacy from the neighbors ASAP, not so good if you’re growing food.

How many mushrooms should you add to a compost? How much is too much?

You don’t want more than 50% of your compost to consist of mushrooms if you’re using said compost in the garden. If you need it for plants that grow indoors (no matter if it’s the greenhouse strawberries or the ficus in your home), don’t go over 25%.

Even if you don’t go over these limits, it would be the best idea to use compost with a lot of mushrooms sparingly. Perhaps only during initial planting or when your plants need extra love and care.

The browns vs the greens

It may be better to use mushrooms as part of your browns and not the greens. Any part of vegetation that can be dried can also be used as a “brown” in a compost mixture.

There’s one simple reason behind it – spores are less likely to survive the drying process. And if you have any spores left behind, they will latch onto something they find yummy in your compost and start growing. Therefore, any leftover raw mushrooms should go through a dehydrator before you chuck them into the composting heap.

Though there’s no need for all these extra steps if you’re just trying to get rid of the leftovers on your plate. Those guys are cleaned and cooked, making them perfectly safe to throw in as a part of your greens.


What should I do if my compost starts growing mushrooms?

Then you start growing mushrooms as well. They are already there, so why not?

Compost can work as a base for growing mushrooms, especially any species that feed on dying and decaying matter. And, fun fact, a lot of edible mushrooms do so.

Of course, this leads to a completely new and different set of issues that need to be addressed, but mushroom growing may be worth the shot. If you already have a green thumb, you’d be pleased to know that they are easier to take care of than anything you tackled before. You can read more about mushroom growing in these articles to see how you can start this new and fun activity.

Though you kinda need to figure out what type of mushroom has sprouted out of your compost and sort of dedicate yourself to it. Mushrooms don’t like to mess with each other’s turf, and you will not be able to rear several species together. Well, unless you want to leave them to battle it out and see which one emerges victorious.

But if mushroom farming is not your new calling, you’ll either need to “rescue” it or get rid of it.

Rescuing the compost

This one will work if you’re dealing with most of the types of fungi, no matter if it’s edible mushrooms or mold. Fingicide.

If you have a large amount of compost that is sprouting something you didn’t want it to sprout, you will need to introduce it to some good commercial fungicide. And that’s the thing you’ll have to pay attention to.

There are a few decent DIY solutions for killing mushrooms, but those should not go near your compost. They are as likely to kill it and the good bacteria in it, as much as they are like to kill the shrooms (think vinegar or bleach).

Walk down to your nearest garden center (or go online) and get a good, commercial fungicide. Make sure that it’s a formula that is safe to use with other vegetation. If you have someone who you can talk to, describe your problem in detail. But, if you’re on your own and shopping online, pick one that comes with a guarantee not to damage your flowers or veg.

Though it could as well be that the situation is not that bad, to begin with. If your mushroom problem did not grow large enough to resemble a forest on top of your compost, you will probably be able to remix everything and balance the mushroom to compost ratio.

This means that if you just finished reading this article and realized that you’ve added too many shrooms to your compost mixture, you can now (or first thing tomorrow) run outside and fix the situation by adding more of your browns and greens. Pretty much, as long as you don’t see new mushroom growth, you’ll be right to assume that you can just readjust your mixture.

However, the troubles start if the thing you managed to develop is mold and not species that are more palatable.


Getting rid of compost

This is a final solution for a compost that is so unusable because of its fungal infestation. Though unexpected growth of the humble button mushroom can be the start of a new adventure, some other fungus can be a death sentence.

Certainly, you should always start by treating the compost with fungicide and giving it a fighting chance, but if you need to repeat that treatment numerous times, it’s time to pull the plug. Obviously, it’s not helping, and you’re adding just more and more unnecessary chemicals to something that is supposed to be “plant food”.

Old compost that was just “used up” can be repurposed in the garden without any issues, but don’t test any of those ideas with this stuff. You will have to get rid of it completely.

You’ll probably have to pass it on to someone who can use it – usually as a construction material. However, before then, treat the whole pile with bleach and kill any of the nasties. People who are taking that stuff off your hands will not look forward to dealing with bacteria, bold, and other fungi.

On the other hand, if you’ve just had an idea of how you can repurpose it for non-planting needs, still remember to sanitize it properly before you start with your project.