Annual, up to over 6 ft. high. Culms erect, stout, often with stilt-roots from the lowest nodes, terete, glabrous, smooth, simple and 4–6-noded below the panicle or occasionally with 1 or 2 mixed branches from the intermediate nodes. Leaves green; sheaths slightly compressed and more or less keeled to terete, tight or at length rather loose, glabrous, smooth, with impressed glands on the keel; ligules short, scarious, rotundate, glabrous; blades linear, moderately attenuated towards the base, long-tapering to a fine point, 1/2 to over 1 1/2 ft. by 2–5 lin., folded with one margin inflexed in bud, then more or less flat, suberect, somewhat stiff or flexuous, glabrous except at the frequently long-ciliate base, rough on both sides (particularly on the upper) and along the margins, midrib slender, becoming stouter towards the base, whitish above, primary lateral nerves 3–5 on each side, prominent, with numerous fine secondary nerves between them. Inflorescence a spatheate panicle of very varying composition, containing few to very many racemes, in more robust plants up to over 1 ft. long and more or less interrupted, occasionally augmented by 1 or several mixed branches; primary internodes few, the lowest up to over 8 in. long, the following rapidly decreasing; lower tiers few-rayed, the following up to 6-rayed, fastigiate, innermost ray sometimes compound and bearing a secondary up to 6-rayed tier; ultimate (simple) rays stoutly filiform, 2 to less than 1 in. long; lowest subtending leaves like the preceding ones, the following becoming rapidly spathaceous with short blades. Spatheoles very narrow, very long-tapering to a slender point, from over 5 to 3 in. long, herbaceous to subherbaceous, glabrous, usually with impressed glands on the middle nerve or keel; peduncle short during flowering, then lengthening out and sometimes only slightly shorter than the spatheole, filiform, appressedly hairy upwards. Racemes stout, compressed-cylindrical, 1–1 1/2 in. long, with 1–3 homogamous and up to 5 heterogamous pairs; internodes of the tough portion of the rhachis under 1 lin. long, glabrous; of the fertile portion (joints) up to over 1 1/2 lin. long, the free upper part 1/2– 3/4 lin. long, widened upwards, obliquely truncate, whitish, glabrous, the part below (callus) as in H. contortus, 1 lin. long; pedicels glabrous, 1/2 lin. long, disarticulating below the middle. Fertile spikelets linear-oblong, terete to subterete, 3 1/4–3 3/4 lin. long (excluding the callus), brown, at length very dark. Glumes equal, coriaceous; lower tightly involute, truncate, minutely and fulvously hirtellous, 7–9-nerved, nerves very fine, faintly visible in transmitted light with very few transverse nerves in the tips; upper glume narrowly linear-oblong, subobtuse, glabrous or nearly so. Lower floret reduced to an oblong hyaline eciliate nerveless valve, 1 1/4 lin. long. Upper floret ♀ or ♂: valve as in H. contortus, 3–5 in. long; valvule lanceolate, hyaline, nerveless, not quite 1 lin. long. Lodicules broad-cuneate, fleshy, 1/2– 3/4 lin. long. Stamens 3; filaments not much longer than the ovary; anthers oblong, purple, 1/2 lin. long or more or less reduced or the stamens quite suppressed. Stigmas exserted from the middle of the spikelet or higher up. Grain linear-oblong in outline, subterete, 3 lin. long, whitish. Male (or neuter) spikelets unequal, green, glabrous, the sessile of the homogamous pairs symmetrical, linear, acute, about 6 lin. long, their lower glume subherbaceous, very closely and finely nerved between the slightly scaberulous keels, inflexed margins equal, very narrow; upper glume slightly shorter, membranous, with 3 green nerves, ciliate upwards; valves and stamens small, rudimentary; the pedicelled of all pairs somewhat asymmetric, lanceolate, subulate-acuminate, 8–10 lin. long, usually more or less contorted; glumes very unequal, lower herbaceous, very closely and finely nerved, with a narrowly winged keel and a fine inflexed flap on one side, and with a keelless involute margin on the other, scrobiculate along a median zone; upper glume as in the sessile homogamous spikelets; valve of lower floret oblong, obtuse, up to over 4 lin. long, 1-nerved, ciliate, of upper floret linear, very narrow, up to 2 lin. long, nerveless, ciliate or both valves more or less (often much) reduced; lodicules up to 1/2 lin. long; anthers up to 2 1/4 lin. long or rudimentary.
