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Houseplant mushrooms are not usually a problem.
However, they need certain conditions to grow (heat, moisture, nutrients), which can cause some houseplants issues.
For example, a mushroom growing in a Calathea pot is likely fine, because they have broadly the same care requirements. A mushroom growing a jade plant could be a sign that the pot and soil are staying wet for too long.
Should I worry if there’s a mushroom in my plant pot?
No, mushrooms in houseplants are typically benign, and don’t mean that there’s anything wrong with your plant.
Mushrooms in your soil can be a good thing, because:
- There are nutrients in your soil
- Mushrooms can improve water retention
- Your humidity levels are good
- Your soil has life
- Mushrooms might improve your soil
- They’re not dangerous to touch
- They won’t harm your plant
- They’re considered lucky by some
Buuut there are potential downsides to having mushrooms in your plant pot:
- Houseplant mushrooms are toxic to eat
- You could be overwatering
- Your soil might lack airflow
A mushroom growing in a houseplant pot isn’t a sign that there’s something wrong with your plant.
The specific species of mushrooms that are likely growing is Leucocoprinus birnbaumii, and they've carved a special niche out of themselves by spreading across the world via houseplants.
I have an article here that will tell you why these mushrooms got into your plant, but long story short, there’s not much you can do to prevent it from happening. The spores have likely been in the soil since the plant was first put in soil.
Houseplant mushrooms: the benefits
It’s not as simple as saying ‘mushrooms in plant soil mean healthy soil’. All we can say objectively is that a houseplant with a mushroom growing in it provides the correct environment for a mushroom.
However, there several things we do know if a mushroom pops up overnight:
There are nutrients in your soil
The species of mushroom that pops up in houseplants can’t grow in a substrate that’s devoid of nutrients.
The spores can germinate, and the mycelium can grow, but the mushroom is like the fungi’s fruit, and it won’t be produced unless there’s a tonne of nutrients in your soil.
They can improve water retention in the soil
Mushrooms like damp environments – that’s why they’re typically found in the leaf litter in forests. If your plant is too dry, then the mycelium won’t be able to grow very well, and you’re highly unlikely to get a mushroom.
If you do tend to underwater your plants, and you still happen to get a mushroom, this is a pretty good indicator that
- someone else is also watering your plants or
- The substrate you’re using is retaining too much water, which can lead to root rot.
Your humidity levels are good
Mushrooms like living in damp soil, but they also like living in humid conditions.
High humidity is only required for the fruit, not the mycelium, and the mushroom can pop up overnight. If you’ve found mushrooms popping up after a night of heavy rain, it’s because the humidity spiked and the mycelium was like ‘guys, it’s time’.
My Monster dubia produced a mushroom when I put it in the bathroom and then had a shower. It’s never produced another since I moved it into the bedroom.
Your soil has life
They eat decaying matter without being annoying (yes, fungus gnats, I'm talking about you), they aerate your soil just by living in it, and they produce nutrient-rich waste so you can fertilise less.
Mushrooms are unlikely to grow if you use a lot of topical pesticides, fungicides, and hydrogen peroxide.
Mushrooms might improve your soil
Emphasis on the word ‘might’.
There isn’t a tonne of research done into the positive impacts on houseplants from Leucocoprinus BUT there are a couple of things that often get mentioned:
- Absorbing carbon from the soil
When we make our own houseplant potting mix, it’s generally recommended that we add things like coir and orchid bark to retain water and add aeration. Both of these products are high in carbon, and our soil mixes tend to be about 20% carbon.
This doesn’t tend to be an issue with houseplants, because the benefits of having well-aerated yet water-retentive soils far outweigh the negatives of growing in an environment that’s too high in carbon.
The fertilisers and soil additives that we use take into account things like the pH of typical houseplant potting mixes, so carbon poisoning isn’t really a thing in houseplants.
But the mycelium of our humble houseplant mushrooms could also be lending a hand. Leucocoprinus birnbaumii can reduce the levels of carbon in the soil by 20% – fungi, in general, are awesome at absorbing excess carbon.
Unfortunately, it’s pretty difficult to work out how much effect the fungi is having on our soil. Leucocoprinus birnbaumii spores have been present in houseplant soil since the 1800s, so they’ve always just been there.
I'm not saying that there are spores in ALL houseplants, but they're extremely common in greenhouses and each mushroom can produce billions of spores, so they're in a large percentage of the houseplants that come from commercial growers.
The fact that there’s never been a major attempt at getting rid of these mushrooms for good definitely points to them being either neutral or beneficial to houseplants.
I cover Mycorrhizal fungi briefly in the main article I wrote on the relationships between houseplants and mushrooms, but the only thing you need to know now is that mycelium (the fungal equivalent of a root system) can attach to plant roots and help the plant absorb water and nutrients.
In return, the mycelium can take carbohydrates from the plant.
It’s a symbiotic relationship that benefits everyone, and actually connects trees and allows them to send messages to each other.
Leucocoprinus birnbaumii is not, from what I can glean, a mycorrhizal fungi, so the mycelium isn’t forming a relationship with the plant’s roots. They’re saprophytic, which means they’re just eating all the decaying matter from your soil.
They’re not dangerous to touch
House plant mushrooms aren’t dangerous to touch, but they ARE toxic to eat. They’ve not been investigated thoroughly with regards to their toxicity level, but they’re classified as ‘medium poisonous’.
This means that if you eat a lot you’ll get a very bad stomachache and will feel very ill, but there are unlikely to be any long term effects unless you’re allergic to them.
In short, don’t eat them.
But there are very few fungi that are poisonous to touch, so as long as you wash your hands well afterwards, feel free to pluck mushrooms from your plant pots without using gloves.
They won’t harm your plant, but they might harm your pets or kids so if you have any of those hanging around, it’s best to get rid of the mushrooms.
They won’t actively harm your plant
Whilst there are species of parasitic fungi out there, Leucocoprinus birnbaumii aren’t one of them. In the wild, they live in the leaf litter of tropical rainforests eating up all the decaying matter.
They won’t damage the roots, they won’t cause any hideous diseases or anything, the mycelium will just chill in the soil, eating nutrients until the conditions are right and they pop up a mushroom.
The mushroom will release spores, and then disappear as quickly as it arrived. And then the cycle repeats.
They’re considered lucky by some
Mushrooms are considered lucky in a number of cultures, most likely due to their almost magical ability to appear and disappear overnight. However, I can’t find any evidence that houseplant mushrooms specifically are found lucky by…anyone – though please let me know if you have information on this.
The Japanese believe Shittake are lucky, the native Americans believe puffballs are lucky and use them in medicine*. A LOT of cultures find psychoactive mushrooms lucky. I couldn’t find anything about Leucocoprinus birnbaumii though.
Though spreading from the tropics to potentially every plant pot in the world seems pretty lucky.
*Apparently in the UK it’s unlucky to collect mushrooms on Sundays. As someone who’s lived her whole life in the UK, and who spent a lot of time foraging as a child, it doesn’t come up often.
Houseplant mushrooms: potential problems
There are a few potential benefits of finding mushrooms in your potted plants, so of course, there are going to be some potential issues too.
Houseplant mushrooms are toxic to eat
We’ve already covered this, but it is important. The mushrooms themselves don’t provide any real benefits to the soil – they’re merely a sign that there’s mycelium present, which potentially improves the soil.
If you have any dependents who might see a mushroom as a tasty treat, remove them (I have an article on how to remove/prevent them here). Don’t worry unduly – a cat or dog would need to consume a LOT of Leucocoprinus birnbaumii to do any real damage but it may still result in a trip to the vet so better safe than sorry.
You will struggle to remove the mycelium without repotting, and it’ll probably return even if you fo repot.
You could be overwatering
Mushrooms will only appear in moist soil.
As I mentioned earlier, mushrooms can pop up in houseplant soil literally overnight, so they could turn up after a watering session.
However, some plants shouldn’t be in soil that stays moist enough to host mycelium – for example, cacti, succulents such as jade plants, and snake plants.
If you do find a mushroom in your snake plant, it's not necessarily a sign that something's wrong, but it's a good indicator that your soil isn't well-draining enough, and you might want to add some sand or something to it.
Mycelium can also increase the amount of water soil can retain, which may cause root rot in plant like cacti.
You don't need to do anything drastic here - in my experience, it's usually a light/warmth issue, rather than a soil issue.
If you increase the light and heat to your cacti the soil will dry out much more quickly and mycelium will reduce.
They eat a lot of nutrients
This isn’t really a negative or a positive – it has the potential to be both, I suppose.
On the plus side, saprotrophic fungi like Leucocoprinus birnbaumii will eat the fungus from decaying matter, like dropped leaves. You will probably also have fungus gnats, which are rarely harmful, but always annoying.
The downside is that they’re also potentially taking nutrients away from your plants. If you fertilise your plants frequently then this won’t be an issue, but if it’s been a few years since you either repotted or fed your plants, then the mushroom’s mycelium is potentially taking the nutrients your plant needs.
Your soil might lack airflow
Mushrooms need oxygen just as much as roots, but they need less than many plants. A lot of climbing aroids, for example, prefer very well-draining soils, which a mushroom wouldn’t really like.
Many people purposefully choose a denser soil mix that can support mushrooms and plants, but if you’re after an airy mix, a mushroom popping up in it might indicate that you need a few more chunks in it.
I often use leca to increase the airflow and water retention of my potting mix, which mushrooms would probably happily coexist alongside.
There are a lot of potential pros and cons to having mushrooms in your houseplants, but it’s impossible to say if a mushroom is a good or a bad sign without first knowing what species the plant is, how much light it’s getting, and what substrate it’s potted in.
Most of the mushrooms in houseplants are totally fine but benign- they’re not a sign that something is wrong or right with the soil…they’re just there.