Eleocharis retroflexa is a small, cryptic grass-like sedge to 10 cm tall. The stems are mostly submerged, 4-angled. The leaves are reduced to a sheath. The flower heads are 2–3.5 mm long, 1–2 mm diameter. The nut is white, c. 0.7 mm long, pitted (Cowie et al. 2000).
Flowering and fruiting: Apr–May.
This species is pantropical in distribution, and in Australia occurs in Queensland and the NT. In the NT, it is known only from two swamps on the Wingate Mountains plateau (Daly River/Port Keats Aboriginal Land Trust) and from a swamp on the sandstone plateau in Nitmiluk NP.
Conservation reserves where reported:
Nitmiluk National Park
Known locations of Eleocharis retroflexa
This species has been reported growing on plateaus, in shallow water on the margins of seasonal swamps. The substrates were laterite or clay loam. Associated species included Melaleuca viridiflora, Eucalyptus phoenicea, Corymbia oocarpa, Capillipedium parviflorum, Sorghum plumosum and Heteropogon triticeus, all common species.
This species is listed as Vulnerable under Federal legislation.
In the NT, this species is coded as Data Deficient based on:
data are considered inadequate for assessment; and
known from three populations, none of which are believed to be under threat.
No abundance data are available for this species and it is considered not adequately surveyed. Although there has been considerable recent botanical survey effort in Nitmiluk NP, the species is inconspicuous. In addition, E. retroflexa appears to have a relatively short flowering and fruiting period, outside of which it would be very difficult to identify. There has been little botanical collecting and only one short general botanical survey in the remote Wingate Mountains since European settlement. All of the sites where it is known could only be accessed by helicopter at the time it was collected.
No threats are known. Parts of the NT where this species occurs are among the most remote and least affected by European settlement. Fire during the April-May fertile period could potentially be a threat. It is possible that high densities of feral stock may affect the species, but there is no information available to demonstrate such threat.
Conservation objectives and management
Further targeted surveys of appropriate habitat at an appropriate time of year are needed to gather distribution and abundance data and assess threats.
Cowie, I.D., Short, P.S., and Osterkamp Madsen, M. (2000). Floodplain Flora: A flora of the coastal floodplains of the Northern Territory, Australia. Flora of Australia Supplementary Series 10, (ABRS, Canberra.)