Xyris capensis is a rush-like herbaceous plant, mostly perennial but occasionally annual, up to 60–300 mm tall, which occurs in clumps. It possesses a weak rhizome. The grass-like leaves are erect and about 50–150 × 4 mm, tapering to hard points and have a fan-shaped arrangement that forms a sheath at the base around the stalk above the small, swollen rhizome. The scapes (leafless flowerstalks) are usually twice as long as the leaves. The flowers are yellow and clustered in a roundish inflorescence of ± 10 mm in diameter, among shiny golden-brown bracts, at the tip of the scape. There are 3 sepals of which two are boat-shaped, whereas the third is membranous and envelops the corolla in the bud. The corolla has a slender tube with 3, spreading, very delicate lobes, which whither quickly, so the flower lasts only a few hours, and 3–5 flowers open at the same time. Flowering is during summer, from November to February.