The opening of the outer layer of the fruiting body in the characteristic star shape is thought to be due to a buildup of calcium oxalate crystals immediately prior to dehiscence.

Initially, the fruiting body is egg-shaped—similar in appearance to puffballs—and has strands of mycelia (rhizomorphs) at the base that attach it to the growing surface.

Unlike some other members of the genus Geastrum (such as G. fornicatum) the arms do not push the basidiocarp off the ground; rather, it lies flat.

[2] The inside of the interior sphere is white when young, but matures into a mass of brown, powdery spores mixed with thick-walled fibres known as capillitium.

[11] Geastrum saccatum is saprobic, and grows scattered or clustered together in leaf litter of humus, usually in late summer and fall.

It is suggested that the mechanism for the antiinflammatory activity is due to inhibition of the enzymes nitric oxide synthase and cyclooxygenase.