Common name: Giant puffball
Description: A white, large, more or less round (it can sometimes be more misshapen than round) terrestrial mushroom, somewhat resembling a large, white a soccer ball resting on the ground. There is no stalk or sterile base, as may be present in other puffballs. The fertile, spore-bearing tissue is on the inside of this mushroom. It is referred to as the “gleba.”
A normal sized puffball may be one to two feet in diameter, but they can get as large as 3 feet (91 cm) in circumference and several pounds/kilograms in weight. When young and choice for eating, the entire gleba/interior of the giant puffball will be completely white. The interior of the mushroom turns a yellowish green as it matures. This discoloration is due to the spores becoming mature—at this stage the mushroom is no longer edible, albeit not poisonous.
Ecology/Associated habitat: The giant puffball is saprotrophic mushroom that decomposes grass litter, detritus and other litter. It is found growing in grasslands such as lawns, meadows, fields, as well deciduous forests. It is sometimes found growing in a circular arrangement commonly referred to as a “fairy ring.” Fairy rings of the giant puffball can be very large, and offer many pounds of mushrooms.
Poisonous look-alikes: There are some mildly poisonous, small, thick-skinned mushrooms, such as Scleroderma species, known collectively as false puffballs. False puffballs are usually dark to dark purple inside, even at a young age, and they all have a thick tough skin.
Tips on harvesting: Only harvest firm, fresh specimens. Harvest by picking, and then brush off any dirt or detritus from the bottom of the mushroom. If you slice a puffball at the stage when it is a choice edible, it will be firm to the touch and the inside will be pure white. If the mushroom is less than firm, the spores inside have likely matured and the inside will be turning a yellowish green. The puffballs are no longer a choice edible at this stage, and should be left outside to let the spores disseminate.
It is best to have a soft-bristled brush with you to brush any dirt or detritus from the bottom of the mushroom. When you find a patch of puffballs, note the location as puffballs are known to come back and fruit in the same location year after year.
Possible allergic reactions and symptoms: There are no reported allergic reactions to this particular mushroom, but allergies to any food are possible. There are those who are allergic to the white button mushroom sold in grocery stores.
As with any wild edible fungus, only try small amounts at first, do not try more than one new species at a time, and be sure to cook your mushrooms thoroughly.
Special considerations for storage: This mushroom is large, so make sure you have room to store all your specimens under refrigeration (it is against Michigan Food Code 3-501.12 to store any food, including mushrooms, above 5oC or 41oF). Further, if stored at room temperature for a day or so, the interior of this mushroom will start to turn yellowish green, indicating the spores are maturing. At this stage, the mushroom is no longer edible.
As with all other mushrooms, store the giant puffball in containers that allow the diffusion of gas (such as paper or cloth bags) and never store any portion of this mushroom in an airtight container such as a zip-lock bag.
Photos:
An edible puffball will be solid white when sliced open
A white and firm giant puffball—the perfect edible stage
A somewhat misshapen giant puffball
References:
Calvatia gigantea at First Nature
Calvatia gigantea at the Kew Botanical Gardens
Calvatia gigantea (Langermannia gigantea) at Rogers Mushrooms
Calvatia gigantea at Wildman Steve Brill’s site
Tom Volk’s Fungus of the Month for August 1998