Flora of the Hawaiian Islands
Monocotyledon Literature for Cenchrus echinatus
Lorence & Wagner, 2019.
   Poaceae -- The Grass Family Bibliography
      Cenchrus echinatus

Common name(s): sandbur, `ume`alu, common sandbur, mau`u kuku
General Information
DistributionNative to the Neotropics, now widely naturalized. In the Hawaiian Islands, naturalized on Kure, Midway, Pearl and Hermes, Lisianski, Laysan, French Frigate Shoals, Nihoa, Ni`ihau, Kaua`i, O`ahu, Moloka`i, Lana`i, Maui, Kaho`olawe, Hawai`i.

Annual; culms decumbent at base, 25‒70 cm tall, profusely branched, compressed, usually geniculate, often reddish at nodes and proximal portion, usually scabrous for 3‒4 cm below panicle, otherwise glabrous.
Leaves with sheath 4‒7 cm long, glabrous or scaberulous, with a conspicuous whitish collar, compressed; ligule densely ciliate, ca. 1 mm long; blade flat, 5‒18 cm long, 3‒9 mm wide, striate, midrib conspicuous, adaxial surface scabrous and sometimes sparsely pilose at base, abaxial surface glabrous or scabrous near apex.
Inflorescences spikelike panicles 3‒7 cm long, rachis zigzag with scabrous angles; burs readily deciduous, contiguous, broadly ovoid, 4‒7 mm long and as wide or wider, bur receptacle obconical, 1‒2 mm long, tomentulose, lobes of bur deeply cleft, short tomentulose, outer series of bristles 2‒3 mm long, retrorsely scabrous, inner series of bristles rather flattened, short pilose at base, retrorsely scabrous toward apex. Spikelets 3‒5 per bur, 4‒6 mm long; first glume membranous, scalelike, indistinctly 1-veined, 1‒1.5 mm long, glabrous, second glume membranous, 4‒4.5 mm long, prominently 3-veined, minutely scaberulous, apex acute; sterile lemma 4.5‒6 mm long, 5-veined, scaberulous, apex acuminate, sterile palea as long as sterile lemma, 2-veined, submembranous, glabrous, apex attenuate; fertile lemma ca. 5 mm long, 5-veined, veins scaberulous near apex, apex attenuate; palea as long as lemma, 2-veined, glabrous, apex acuminate.
Caryopses broadly ovate, usually flattened ventrally, rounded dorsally, 3‒4 mm long.
2n = 34, 68.
Nancy Khan