Tom Volk's Fungus of the Month for March 2003

This month's fungus is Marasmius oreades, the fairy ring mushroom.
It's my 75th FotM!

For the rest of my pages on fungi, please click

Marasmius oreades fairy ring

This month's fungus is famous for forming "fairy rings" in the grass. And since St. Patrick's Day leprechauns are really just a very butch type of fairy, it's appropriate to have the fairy ring mushrooms as this month's fungus. I'll tell you more about fairy rings later.

Marasmius oreades is considered to be a relatively delicious edible mushroom. However, I am not particularly enamored by its flavor or texture. It's just "okay" in my book. I have seen a recipe for cookies made from this mushroom-- in Hope Miller's wonderful mushroom cookbook. You can search your favorite bookstore to find this book or go directly to the publisher at Mad River Press. In any case the fairy ring mushroom does have a kind of crunchy texture. You should try it at least once, maybe in a stir fry or omelette. You can write to me if you find a more interesting way to prepare this mushroom. Before you eat this (or any) mushroom, you should, of course, take note of the environment in which you find this mushroom growing. Any mushroom growing in heavily pesticided or herbicided lawns should not be eaten. This is particularly important on golf courses, which are some of the most heavily "chemicalized" environments known-- there's nothing at all natural about most golf courses. You should not eat a mushroom unless you're sure of the conditions of the substrate on which it's growing. Many fungi accumulate toxins and get rid of them by shunting them above ground into their fruiting bodies. Be careful!

Marasmius oreades close-upMarasmius oreades is interesting in several other ways. The most interesting phenomenon is that it can dry out and revive many times. Compare this to other mushrooms that fruit once and they're done. They cannot revive even when given adequate water. You can learn more about this phenomenon from Steve Saupe at St. John's University in Minnesota on his page called The Biology of Resurrection: Life After Death in Fungi. Apparently Marasmius species are able to withstand drying out because of a high concentration of trehalose, a type of sugar. The trehalose apparently acts as a xeroprotectant for the fungus, preventing damage as the cells dry out. When water is added back to the mushrooms, the trehalose is digested as the cells take in the water and revive. It has been proven that Marasmius is actually alive, not just swollen up when rehydrated-- it undergoes cellular respiration and can grow and produce new cells after revival. Marasmius fruiting bodies are able to begin producing spores again whenever there is enough water to make spore germination and hyphal growth possible. Thus Marasmius not only increases its surface area for bearing spores by forming gills, it also effectively increases its surface area over time by being able to dry out and revive several times. You can read more about surface area and reproduction starting here.

This resurrection occurs in many other fungi, especially in the resupinate crust fungi (Corticiaceae). See this page for some examples. Most of these fungi produce fruiting bodies that are very flat, and thus have no physical way of increasing their spore bearing potential. However,they can dry out and revive many times during a season, or over the course of a few years, effectively increasing the number of spores a single fruiting body can produce. It's a very effective way of conserving energy, since it's very expensive (in terms of ATP) to produce fruiting bodies.

The growth pattern of Marasmius oreades is also interesting. It almost always grows in a circular pattern, commonly called a fairy ring. Fairy rings got their name in the olden days in Europe, when people came upon these rings of mushrooms in clearings and meadows in the woods. Obviously there must have been some fairies or wood nymphs (or leprechauns) doing their magical dances during the night, in and out of these fairy rings. You can understand the circular growth of the fairy ring by thinking about what happens when a fungus spore lands on your bread or your cheese or your jello-- it germinates then grows in every direction it can. If the substrate is perfectly homogenous, i.e. composed of exactly the same nutrients throughout, this will result in a perfect circle. Slight variations in the substrate can account for different growth rates in different parts of the circle, making it less than perfectly round. Interestingly, if you try to isolate the fungus from the far inside of the circle, you will find that the fungus is no longer growing there, but only on the outside edge. You can also notice the center of the fairy ring is often quite differently colored from the outside of the ring, adding to its mystique. In reality, the colors are different because the fungus has used up the nutrients in the center, thus negatively affecting the growth of the grass in the immediate area where it's growing. As the fungus dies off in the center, it returns nutrients to the soil, eventually positively affecting the grass growth. Although they can occur almost anywhere, fairy rings are most often seen in lawns and other grassy areas where the substrate is relatively homogenous. Some other fungi commonly grow in fairy rings, including Chlorophyllum molybdites and Calvatia gigantea.

ahhh, always after me Lucky Charms...

I hope you enjoyed learning something about Marasmius oreades today. There are lots of interesting phenomena associated with this mushroom, including resurrection and fairy rings.

For your enjoyment, here's an image of everyone's favorite leprechaun, on the Lucky CharmsTM Box-- the way the leprechaun WISHED it was...

Can you name all of the leprechaun's favorite fungi? You can click on each magically delicious marshmallow for more information.

If you have recommendations for future FotM's please write to me at Or maybe you'd like to be co-author of a FotM?

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 2003 by Thomas J. Volk, University of Wisconsin-La Crosse.

Return to Tom Volk's Fungi Home Page

Return to Tom Volk's Fungus of the month pages listing Marasmius oreades Trametes versicolor Morchella esculenta Amanita muscaria Saccharomyces cerevisiae Aspergillus just a green marshmallow mushroom just a mushroom rainbow marshmallow just a marshmallow heart