Cenchrus echinatus L.

synonyms: Cenchrus echinatus var. hillebrandianus, Cenchrus hillebrandianus


sandbur, ‘ume‘alu, sunbur, pokies


Info

Subfamily: Panicoideae
Genus etymology: Cenchrus = "millet" [Greek]. However this is a misnomer, the only millet species in this genus is C. americanus, and this was treated as Pennisetum when Cenchrus was erected.
Species etymology: echinatus = "hedge hog" [Latin] refering to the spines on the burs
Photosynthetic type: C4 (warm season)
Nativity: naturalized - accidental
First recorded in Hawaiʻi: 1864

Map

 Distribution of Cenchrus echinatus in Hawaiʻi.
 Distribution of Cenchrus echinatus in Hawaiʻi.

Inflorescence

Cenchrus echinatus Inflorescence
Cenchrus echinatus Inflorescence
Cenchrus echinatus Inflorescence
Cenchrus echinatus Inflorescence
Cenchrus echinatus Inflorescence

Plant

Cenchrus echinatus Plant

Habit

Cenchrus echinatus Habit
Cenchrus echinatus Habit

Spikelets

Cenchrus echinatus Spikelets
Cenchrus echinatus Spikelets
Cenchrus echinatus Spikelets

Description

Plants annual. Culms 20-100 cm, ascending from a geniculate base. Sheaths from shorter than to equaling the internodes, compressed; ligules 0.7-1.7 mm; blades 4-18(35) cm long, 2-10(14.2) mm wide, adaxial surfaces sparsely pilose, hairs papillose-based. Panicles 2.5-12 cm; rachis internodes 2-4 mm; fascicles 5-10 mm long, 3.5-6(6.3) mm wide, imbricate; outer bristles 10-20, terete, the majority no more than 1/2 as long as the inner bristles; inner bristles 2-5 mm long, 0.6-1.5 mm wide, flattened, not grooved, mostly erect, fused for at least 1/2 their length into a globose cupule, sometimes interlocking at maturity, shortly pubescent, often purple at maturity. Spikelets 2-3(4) per fascicle, 4.8-7 mm. Lower glumes 1.3-3.4 mm; upper glumes 3.8-5.7 mm, 3-7-veined; lower lemmas 4.5-6.5 mm; upper florets 4.7-7 mm; anthers 0.8-2.4 mm. Caryopses ovoid, 1.2-3.2 mm long, 1.3-2.2 mm wide. 2n = (34), 68.
(Description source: Barkworth, M.E., Capels, K.M., Long, S. & Piep, M.B. (eds.) 2003. Flora of North America, north of Mexico. Volume 25. Magnoliophyta: Commelinidae (in part): Poaceae, Part 2. Oxford University Press, New York. 783 pp http://floranorthamerica.org/Cenchrus_echinatus )

Annuals; culms decumbent at base, 25- 70 cm tall, profusely branched, compressed, usually geniculate, often reddish at nodes and lower portion, usually scabrous for 3-4 cm below panicle, otherwise glabrous. Sheaths 4-7 cm long, glabrous or scaberulous, with a conspicuous whitish collar, compressed; ligule densely ciliate, ca. 1 mm long; blades flat, 5-18 cm long, 3-9 mm wide, striate, midrib conspicuous, upper surface scabrous and sometimes sparsely pilose at base, lower surface glabrous or scabrous near apex. Inflorescences composed of racemes 3-7 cm long, rachis zigzag with scabrous angles; burs usually dark red to purple, readily deciduous, wellspaced, 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, scale-like, indistinctly 1-nerved, 1-1.5 mm long, glabrous, second glume membranous, 4-4.5 1513 mm long, prominently 3-nerved, minutely scaberulous, apex acute; sterile lemma 4.5- 6 mm long, 5-nerved, scaberulous, apex acuminate, sterile palea as long as sterile lemma, 2-nerved, submembranous, glabrous, apex attenuate; fertile lemma ca. 5 mm long, 5-nerved, nerves scaberulous near apex, apex attenuate; palea as long as lemma, 2-nerved, glabrous, apex acuminate. Caryopsis broadly ovate, usually flattened ventrally, rounded dorsally, 3-4 mm long. [2n = 34, 68.]
(Description source: O’Connor, P.J. 1990. Poaceae, pp. 1481–1604. In: Wagner W.L., Herbst D.R. & Sohmer S.H. (eds.)., Manual of the flowering plant of Hawaiʻi. Vol. 2. University of Hawaii Press & Bishop Museum Press, Honolulu )