Smooth, often cespitose, annual or short-lived perennial, 10-100 cm high; stems short. Leaves erect or in a fan, 10-60 cm, sheath often as long as blade, entire, with or without a short ligule; blades flattened, 2-10 mm wide, margins mostly thin, smooth or papillose. Scapes distally terete or oval, 1-1.5 mm wide, multistriate and 1-2-ribbed, ribs strong, usually papillose-tuberculate; spikes ovoid to short-cylindric, 0.5-1.5 (-2.5) cm, bracts many in a spiral, lowest ones empty, grading larger into the flowering ones, these obovate to ovate, 5-7 mm, apically rounded to subacute, mostly entire, convex, ecarinate, dorsal area evident. Lateral sepals equilateral, narrow, slightly curved, 3-7 mm, keel broad, lacerate from middle to apex; petals broadly obovate, 3-5 mm; staminodes bearded; anthers ca.1.5 mm. Capsule 3-4 mm long, placentation parietal; seeds broadly ellipsoid, 0.4-0.5 mm, pale amber.
Andean Colombia present, Andes present, Argentina present, French Guiana present, South America present present, Trinidad present, in North America through the Atlantic and Gulf Coastal Plain into adjacent provinces present
In South America from Andean Colombia eastward to French Guiana and Trinidad, and southward through South America E of the Andes to Argentina; in North America through the Atlantic and Gulf Coastal Plain into adjacent provinces.
This is morphologically and ecologically the most variable
Xyris in the New World, being adapted to wide ranges of substrate and soil aci- dity. It is thus one of the truly weedy xyrids, coming abundantly around artificial bodies of water, along ditches and in moist fields and wet pasture. It is nearest both in form and ecology to the only slightly less weedy X. laxifolia, and unfortunately many collectors sample both under the same number; thus both species end up on the same herbarium sheet. This is even true of some of the type material of both species, and this has led to various interpretations of said types. X. jupicai, however, tends to be annual, more slender, is lower, its bases stramineous or greenish, its scape ribs papillose distally, its spikes range smaller, its seeds shorter, of broader outline, are translucent. Thus where mixed populations are found, X. laxifolia stands out as coarser, taller, usually with red or purple pigmentation, reddening the plant base and darkening the green of the leaf blades, with broader, longer, smoother scapes, larger and darker spikes; its seeds are longer and narrower in outline, and usually farinose.