Schoenus calceolus
A unique diagnostic character of "S. calceolus" is the flat culm bases held together by a thin translucent sheath, which can sometimes be twisted. "Schoenus calceolus" has ovate spikelets that are similar in form to those of "Schoenus prophyllus" and "Schoenus purpurascens". Compared to the wider, non-channelled leaves of "S. purpurascens", those of "S. calceolus" are channelled and more slender. In addition, "S. calceolus" has less firm prophylls that are not shiny in contrast to the shiny and relatively long prophylls of "S. prophyllus". The prophyll mucros (awns) of "S. prophyllus" are relatively long (>3.0 mm) compared to the relatively short mucros (<2.4 mm) of "S. calceolus".
"Schoenus prophyllus" often grows in close proximity to "S. calceolus", but the flattened culm base and straight leaves of the latter species differ from those of "S. prophyllus", whose leaves curl with age. Similar to other sedges, plants in this group are very difficult to identify. It appears that part of this problem is caused by the tendency of the southern African "Schoenus" to form hybrids with each other. It is not clear whether "S. calceolus" forms hybrids with other southern African "Schoenus" species. "Schoenus calceolus" is a species in family Cyperaceae, tribe Schoeneae. Other genera in tribe Schoeneae include "Lepidosperma", "Oreobolus", "Costularia", "Tetraria" and "Gahnia". The most closely related species to "S. calceolus" are other southern African "Schoenus" species, specifically, species in the "S. cuspidatus" and allies group growing in close geographic proximity. Southern African "Schoenus" were once classified as "Tetraria"; however, based on molecular and morphological differences, the two groups are evolutionary distinct. To ensure that this group of sedges is monophyletic (i.e. the genus only has closely related species), several species of "Epischoenus" and the southern African "Tetraria" were transferred into "Schoenus". In the field, the southern African "Schoenus" can be distinguished from "Tetraria" species by their lack of stem leaves and the absence of reticulate sheaths at the bases of the flowering stems. "Schoenus calceolus" is a species from the Agulhas Plain region of South Africa. It is primarily a species of limestone-derived soils, growing at elevations below 150 m.
Distribution and habitat
Schoenus calceolus is a species of sedge endemic to limestone-derived soils in the Agulhas Plain region of South Africa.