They are poorly drained, slightly acid to moderately alkaline in pH, and contain litle organic matter. In Missouri, the soils are Entisols just beginning to form over sandstone outcrops. A population in Dade Co., Missouri occurs in a roadside ditch and could be impacted in the future by the results of certain maintenance practices, such as drift from herbicide use. Anthesis occurs during March and April in Arkansas and in April and May in Missouri. It is not known how pollen is disseminated.
Most pollination probably occurs by selfing, though ants are possible pollinators.
Geocarpon is limited to open areas with little competition from other species. In Missouri, Geocarpon grows in moist pockets of generally drier, sandy soils on exposed sandstone outcrops of the Channel Sands formation. Geocarpon appears to have a high light requirement and tolerates little or no competition by other species. Species diversity is low in these communities. Arkansas sites of Geocarpon characteristically have prominent blue-green algal colonies in close associaton at anthesis.