Tom Volk's Fungus of the Month for February 2002

This month's fungus is Leucocoprinus birnbaumii, aka Lepiota lutea, the yellow houseplant mushroom.

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Leucocoprinus with a potted plant Leucocoprinus birnbaumii (luke-o-kuh-PRY-niss burn-BAUM-eee-eye) is a common mushroom in house plants and greenhouses or any other place with organically rich soil where the temperature is warm . I get lots of emails about this particular fungus in the winter, so I thought that it's about time to make it the Fungus of the Month. It's a bright colorful mushroom that helps those of us in the far north get through the long, mostly mushroomlesss winter. It's also very common in the south in warmer climates, where it can grow outdoors, especially in mulched flower beds.

I get *lots* of email about this fungus. In the table below I've put a small sampling of some of these interesting emails. You'll notice, however, that they start to sound the same after the first few. That's why I made Leucocoprinus birnbaumii this month's Fungus of the Month.

Recently while I was watering plants in my house i noticed, bright canary yellow mushrooms growing from the dirt, the stems are tapered and thin toward the cap, the cap is covered with a almost pollen-like substance, the largest is approx. 5 in. could you possibly identify it ? I hope the picture helps.

I hate to bother you but my 13 and 8 year old daughters are fascinated by what we believe to be mushrooms growing in our bathroom in a plant we have had for two years. They started out small and yellow but there growth over the past 24 hours has been amazing. They started showing up a few months ago and i would just throw them out until the other day my daughters said to let them grow to see what happens. Those mushrooms were all we could talk about at dinner. Please we have to know what they are.

They are bright yellow with a thin stem and a round head. The lights are never out in the bathroom and the plant gets plenty of water. We need to know in Philadelphia, PA.

Hello, Professor Volk. I found your website when looking up "fungi" on, after my girlfriend and I found a bizarre fungal growth in one of our plants. More specifically, it was between the plastic planter

the plant (a small Ficus tree) came in and the slightly larger plastic planter which we have been putting off re-planting the tree into. We've had the tree in the two planters for months, but just this morning we noticed the strange yellow growths peeking up from between the planters.

When I removed the tree from the larger planter, we found that the growths were actually the tops of the caps of several large mushrooms. They were of an intense yellow hue. They were attached to the smaller planter, growing out from the bottom rim of it.

We'd like to know what this was (and whether it could have been or was dangerous to us or our cats, etc.). We took a picture, which as it was on film and not digital we will have to wait to get developed before I can send it to you. This fungus was a strange discovery, particularly because of its intense color. We would appreciate any insight you could share with us as to its origins and toxicity.

I have a bright yellow cespitose fungi growing in the dirt of my fig tree in my house. It begins as a yellow-white fuzzy film and then shoots out about two inches high with the stems/stalk about 1/4 inch in diameter with the appearance of a cap not much bigger than the stem itself. Any clues as to what it is and how I get it out of the dirt without killing the plant. I know
I could just repot. But if it is not harmful can I leave it ... any suggestions are welcome.

Hey, I was just trying to do some research on this phenomena I have. I just noticed the other day that there are two yellow mushrooms sprouting from a houseplant I bought for my apartment about five months ago (I think the plant is a type of fern). I was wondering if this has anything to do with the water with which I water the plant or fungus in the apartment in general (we keep the place very clean). They are a suspicious yellow that I thought could be poisonous. You have any thoughts?

I am having a problem of what seem to be mushrooms growing in my pot that I have a cane like plant growing it. In my country, The Bahamas, they are what we commonly refer to as "spirit umbrellas".
Why are these mushrooms growing in my plant pot and what is causing them. I have my plant on the inside.

We have a fungus growing at the base of one of our plants at the office. They were growing under some bark chips. There is currently a little clump of 10 or so heads. They are very short right now, maybe a half inch, but they are quite pointed (not a flat or rounded cap) but will grow several inches tall. And they are bright fluorescent yellow. No discernable spots or anything else like that. I wanted to find out if they were poisonous or potentially dangerous. Can these be touched without gloves?

Leucocoprinus in a potted plant with shellsLots of interesting emails. My favorites from above are the family endlessly discussing during dinner the yellow mushrooms in their bathroom, and the email from the Bahamas calling them "spirit umbrellas." very cool

To answer the several common questions: The mushrooms are not known to harm plants either and likely came in with the potting soil. There are conflicting reports about the toxicity of this fungus, with some evidence that it causes gastrointestinal upset in a very small percentage of people and other animals. However, you would likely have to eat several dozen of them for any effect. However, I advise that you do not eat them. I recommend to people to just leave the mushrooms alone and enjoy them, as they are very unlikely to cause any problems. Besides it will give you something to talk about during dinner.

One common misconception, as mentioned in one of the above emails, is that you can be poisoned by a mushroom by just touching it. This is completely false, unless you are allergic to the mushroom. In a very few cases with very few types of mushrooms with a very small percentage of people, some mushrooms (notably Suillus americanus, which only grows with eastern white pine, Pinus strobus) can cause an allergic dermatitis, with a mild skin rash. It is ok to handle even the most poisonous mushrooms, such as the death angels. You would have to ingest several grams of these mushrooms for poisoning to occur; it is just not possible to absorb this amount through the skin.

Leucocoprinus young and oldYou have probably heard of the more common genus Coprinus, the inky cap mushrooms. Since you've already read about Leucopholiota and Pholiota, you might guess that LEUCOcoprinus should be a white spored Coprinus. In fact they do look very similar, although Leucocoprinus never undergoes autodigestion or autodeliquescence as Coprinus does. It's not clear how closely related Coprinus and Leucocoprinus are. Someone probably knows, but I haven't seen it in the literature yet. You can think of an analogous situation with the brown-spored Agaricus and the white spored Leucoagaricus. which have already been shown to be closely related. Most researchers, however, believe that Leucocoprinus is related to the genus Lepiota, which in turn is closely related to Agaricus (Agaricaceae), in a different family from Coprinus in the broad sense (Coprinaceae or Psathyrellaceae). There's a whole grand story behind the last sentence, which I won't get into just now...

You'll notice from the picture on the left that the mushrooms start out as a very bright yellow color. This color fades out to a very pale yellow (almost white) as the cap expands to release the spores. You can see that there are at least 20 very small yellow primordia waiting to expand.

The last time I visited the Missouri Botanical Gardens they had a display of tropical foliage with bright green tree frogs and these bright yellow Leucocoprinus. It made for a very striking and beautiful display. I was not sure if they had put the mushrooms into the terrarium on purpose. but they should have...

I hope you enjoyed learning something about Leucocoprinus birnbaumii today. There are lots of unexpected beautiful pleasures in life. In the winter in the north we take what we can get. But I'd be happy to see these beautiful mushrooms anytime.

If you have anything to add, or if you have corrections or comments, please write to me at

This page and other pages are © Copyright 2002 by Thomas J. Volk, University of Wisconsin-La Crosse.

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