Tom Volk's Fungus of the Month for August 1998

This month's fungus is Calvatia gigantea, the giant puffball

See also this page of fun things to do with giant puffballs

For the rest of my pages on fungi, please click

Calvatia gigantea with American quarter, which is about an inch across This month's fungus is the giant puffball, Calvatia gigantea, known (as you might guess from the specific epithet) for its large size. Plus when you find an immature specimen that is pure white inside you've found a delicious edible mushroom! It can grow to be quite large-- I've collected specimens more than a meter in diameter! This is pretty impressive for a fungus that produces its fruiting body in just a week's time. Unlike most mushrooms, however. the basidiospores of Calvatia are borne inside the fruiting body-- a large fruiting body may contain billions of spores! Calvatia belongs to a class of fungi known as the Gasteromycetes-- literally "stomach fungi" --- because they all bear their spores internally. The Gasteromycetes all have basidiospore maturation prior to the spores being exposed to the air. in addition there is no fertile layer of basidia, as in the Hymenomycetes, the class to which most of the familiar fungi belong. The basidiospores of the Hymenomycetes are also forcibly discharged, unlike the Gasteromycetes, which must have their spores dispersed by some outside force, usually wind, rain, bacterial or fungal degradation, or animals such as insects.

When the basidiocarp is young you can do a section through the gleba (the white inside part of this fruiting body) and observe the glebal chambers, which are lined with basidia and basidiospores. As in most Gasteromycetes, the gleba disintegrates as the spores darken and mature. 

Diane Derouen with a giant puffballYou may have seen another scientific name for this fungus, Langermannia gigantea, showing up in some recent books and field guides. You'll be glad to know we donít have to use this old, rediscovered name. According to the 1992 International Code of Botanical Nomenclature, which governs the name of all plants, fungi and lichens, the name Calvatia has been conserved over the older name Langermannia, thus meaning we can (and should) use as the genus name for this fungus. The picture is Diane Derouen of the Botany Dept at UW-Madison holding a large specimen of Calvatia gigantea
Despite its name, Calvatia gigantea pales in size comparison to fruiting bodies of another fungus,Bridgeoporus nobilissimus, the giant polypore of the Pacific Northwest. You can read about it and see it by clicking here
part of a Fairy ring of 53 giant puffballspart of a fairy ring of Calvatia giganteaOnce in a while you can be very lucky and find lots of these things. Several years ago in southern Wisconsin I found a fairy ring of 53 (fifty-three!) giant puffballs. All but one of them were in the prime edible stage. The picture to the left is part of that fairy ring. It was impossible to take a picture of the entire ring because of all the trees and plants inside the 15 meter diameter of the nearly complete ring. The picture to the right is my attempt at photographing the ring-- I partially climbed a tree and temporarily bent down some of the larger plants in t he center of the ring to get this picture, but it's still somewhat less than adequate-- but it does give you the idea of its impressive large size. I went back several time the next year to see the ring, but only found 5 or 6 fruiting bodies total for the year. Conditions must have been just exactly right for the formation of that large ring!

So how and why does a fairy ring form? Think for a minute about the way a fungus grows on a piece of bread on your countertop-- the colony is very circular, with the fungus spreading out in two dimensions on the top of the bread. It's a little more complicated for a fungus in the woods. The substrate is not so homogenous,, but the colony of the Calvatia must have been inoculated in the center several years before. Usually the center of such colonies dies and the only living part is around the outside edge, where the fruiting bodies then form. Fairy rings can be more easily seen in the more consistent environment of a lawn, where one can often see fairy rings of Agaricus campestris, Calvatia cyathiformis, Chlorophyllum molybdites, or *the* fairy ring mushroom, Marasmius oreades. Sometimes you can find a lawn with several overlapping rings of several different species. Very impressive! 

Lycoperdon pyriforme, the pear shaped puffballAnother member of the Lycoperdales that you have probably seen in the pear-shaped puffball, Lycoperdon pyriforme. This species disperses its basidiospores through a small hole that is digested in the top of the fruiting body-- the familiar "puff" of the puffball comes from squeezing or tapping the fruiting body-- or naturally due to the force of raindrops hitting their outside. These smaller puffballs are also edible, provided they are growing on wood, have a thin skin, and are pure white inside. 

Scleroderma citrinumThe giant puffballs are generally considered to be edible. But there are some things you have to watch out for. Especially a problem are the false puffballs, Scleroderma species. The false puffballs all have a thick tough skin and are generally dark inside (the gleba) even from a young age. They are not severely poisonous, causing a somewhat unpleasant gastrointestinal upset. Fortunately most of them are small. less than 15 cm diameter. The tough skin and unpleasant flavor ensures that few people have been tempted to eat this fungus. The species shown here is probably Scleroderma citrinum, the poison pigskin puffball. 
So get out there in the woods and start looking for Calvatia gigantea. Maybe you'll find some smaller species such as Calvatia craniformis or Calvatia cyathiformis. If youíre in the western part of North America you might find the very large Calvatia booniana. If you find these, I suggest preparing by slicing the pure-white fruiting body into rectangular strips, dipping it in egg, then bread or cracker crumbs, and then frying it in butter and/or olive oil until they're golden brown. Delicious-- and with a very interesting texture! Happy hunting! 

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