Eleocharis palustris; The Slender Spike-rush is middle-sized spike-rush (culms are more or less 10 centimeter tall). The spikelets are rather dark and glossy. Like all other Eleocharis species, it grows on wet soils. Differentiating features to other closely related species can be found on the page of Eleocharis palustris (Common Spike-rush).
It is a member of the sedge family (Cyperaceae). The Icelandic name of this species is Vætuskúfur.