Geastraceae

The earthstars are the family Geastraceae of gasterocarpic basidiomycetes (mushrooms). It includes the genera Geastrum and Myriostoma. About 60 species are classified in this family, divided among 8 genera.

Older classifications place this family in the order Lycoperdales, but more recently they have been placed in Phallales.

One member of this family, Sphaerobolus stellatus, is a nuisance organism in landscapes known as "shotgun fungus" or "cannonball fungus", which colonizes wood-based mulches and may throw black spore-containing globs onto nearby painted surfaces.

Many of these fungi behave in the following manner: In dry weather the "petals" will dry and curl up around the soft spore sac, protecting it. Often the whole fungus in this state becomes detached from the ground and can roll around like a tumbleweed. When the weather dampens the "petals" moisten and uncurl and some even curl backwards lifting the spore sac up. Presumably this then allows rain or animal movement to hit the spore sac so that it will puff out spores when there is enough moisture for them to germinate.