Plants annual or perennial; scrambling. Culms 0.5-2 m, ascending to decumbent, often rooting at the nodes, branched. Leaves not aromatic; sheaths open, at least the outer margins pubescent, usually with papillose-based hairs; ligules membranous, fimbriate or ciliate; blades ovate to ovate-lanceolate. Inflorescences terminal and axillary, panicles of subdigitate, often flabellate, clusters of rames; rame internodes not sulcate; disarticulation in the rames, beneath the sessile spikelets. Spikelets in heteromorphic sessile-pedicellate pairs or appearing solitary and sessile, pedicels greatly reduced and lacking spikelets. Sessile spikelets bisexual, with 2 florets; calluses absent or blunt; glumes equal or subequal; lower florets sterile, reduced to an unawned lemma; upper florets bisexual, awned (rarely unawned); anthers 2 or 3. Pedicels 0.2-3 mm, not thickened, not fused to the rame axes. Pedicellate spikelets absent or rudimentary. x = 9, 10. Name from the Greek arthron, segment, and axon, axis, referring to the jointed inflorescence axes.

Arthraxon is a genus of seven species that are native to tropical and subtropical regions of the Eastern Hemisphere; one species is established in the Flora region.

1.   Arthraxon hispidus (Thunb.) Makino
Jointhead, Small Carpetgrass

Plants annual. Culms 0.5-1(2) m, weak, often decumbent and rooting at the lower nodes; nodes hispid. Leaves cauline; sheaths usually shorter than the internodes; ligules 0.4-3.5 mm, ciliate; lower blades 1-7.5 cm long, 4-20 mm wide, cordate-clasping, ovate to ovate-lanceolate, flat, margins ciliate (sometimes sparingly so), surfaces usually glabrous, abaxial surface rarely hispidulous; upper blades greatly reduced. Panicles 1.3-7 cm, flabellate or contracted, with 12-20 rames; rames 1-6(11) cm. Sessile spikelets: glumes 3-5.5 mm, lanceolate; lower glumes several-veined; upper glumes 1- or 3-veined; awns 0.3-9 mm, included or exserted, usually twisted below, sometimes geniculate at midlength; anthers usually 2, 0.5-0.7 mm. Pedicels absent or to 2 mm. Pedicellate spikelets absent. 2n = 36.

Arthraxon hispidus is native to Asia, but is naturalized and spreading along roadsides, shores, ditches and in low woods and fields of the eastern United States. It is also naturalized in Mexico, Central America, and the West Indies. Plants in the Flora region belong to A. hispidus (Thunb.) Makino var. hispidus, the most widespread and variable of the four varieties. Arthraxon castratus (Griff.) V. Naray. ex Bor, reported from Puerto Rico, differs from A. hispidus in having pilose lemma margins, a palea in its second floret, and three anthers.