Schoenus adnatus is a species of sedge endemic to mountainous locations in southern regions of South Africa.

[1] The main important character distinguishing S. adnatus from other similar species is that the spikelet receptacle is adnate to the lowest (basal) glume (bract).

[2] It is impossible to determine if S. adnatus forms hybrids with other southern African Schoenus species because of a lack of evidence.

[1] The southern African Schoenus were previously included within the genus Tetraria; however, we now know that the two groups are evolutionary distinct based on molecular and morphological differences.

[7] Few recent field collections of S. adnatus exist,[1] meaning that it has been impossible to study its evolutionary relationships with the Epischoenus group of Schoenus.