Andreaea has a unique position on the phylogenetic ladder of mosses. The capsules of Andreaea open by 4 slits along the length of the capsule. Unlike moss other mosses which have capsules borne on true stalks (setae) consisting of sporophytic tissue, the capsules of Andreaea are borne on structures called pseudopodia, which is a stalk of leafless gametophytic tissue. The only other group of mosses with such a structure is Sphagnum.

Andreaea spp. are almost always restricted to rocks, especially in alpine or subalpine environements. The shoots of some species can attain great lengths, especially when submerged.