Moist sandy, mucky, or boggy shores of a large number of small lakes in the southwestern Lower Peninsula, especially by receding lakes, in somewhat acidic soils. 

A species of disjunct distribution, with virtually no stations between Michigan and northern Indiana and the Coastal Plain. The culms are dimorphic, some of the vegetative ones elongating, arching, and tip-rooting. Plants lacking achenes may thus resemble E. rostellata, from which they may be easily distinguished by the presence of a definite narrow tooth (up to 1 mm long) at the summit of the leaf sheath in E. melanocarpa; in E. rostellata the sheaths are truncate with at most a callus swelling. The habitats are quite different as well, with E. rostellata being a calciphile.