Michael T. Stieber and J.K. Wipff

Plants annual or perennial. Culms 5-200 cm, erect or decumbent, usually geniculate; nodes and internodes usually glabrous. Sheaths open, usually glabrous; ligules membranous, ciliate, cilia as long as or longer than the basal membrane; blades flat or folded, margins cartilaginous, scabridulous. Inflorescences terminal, spikelike panicles of highly reduced branches termed fascicles ("burs"); fascicles consisting of 1-2 series of many, stiff, partially fused, usually retrorsely scabridulous to strigose, sharp bristles surrounding, sometimes almost concealing, 1-4 spikelets; outer (lower) bristles, if present, in 1 or more whorls, terete or flattened; inner (upper) bristles usually strongly flattened, fused at least at the base and forming a disk, frequently to more than 1/2 their length and forming a cupule; disarticulation at the base of the fascicles. Spikelets sessile, with 2 florets; lower florets usually sterile; upper florets bisexual. Lower glumes ovate, scarious, glabrous, 1-veined, acute to acuminate; upper glumes and lower lemmasovate, 3-9-veined; lower paleas equaling the lemmas, tawny or purplish; upper lemmas and paleas subequal, indurate, ovate, obscurely veined, acuminate. Caryopses obtrulloid. x = 17. Name from the Greek kengchros, millet.

Cenchrus has about 16, primarily tropical species, most of which are readily (and painfully) recognized by their spiny fascicles. Most of its species differ from those of Pennisetumin having retrorsely scabrous or strigose inner bristles that are fused to well above their bases. The species are generally considered to be undesirable weeds.

Seven species of Cenchrus are native to the Flora region. The eighth species in this treatment was collected once in Westchester County, New York, but does not appear to have become established in the Flora region.

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SELECTED REFERENCES Chase, A. 1920. The North American species of Cenchrus. Contr. U.S. Natl. Herb. 22¹:45-77; DeLisle, D.G. 1963. Taxonomy and distribution of the genus Cenchrus. Iowa State Coll. J. Sci. 37:259-351; Gayle, E.E.1892. The spines of Cenchrus tribuloides L. Bot. Gaz. 17:126-127; Sohns, E.R. 1955. Cenchrus and Pennisetum: Fascicle morphology. J. Wash. Acad. Sci. 45:135-143.

T.A. Cope (1993) Poaceae Flora of Somalia 4: 148-270

NOTE: This description has been modified to reflect the inclusion of Cenchrus and Pennisetum in a single genus which, in accordance with its nomenclatural priority, is called Cenchrus. 

Plants annual or perennial. Leaves linear to lanceolate, flat or inrolled; ligules usually a line of hairs, rarely a membrane. Inflorescences spikelike, cylindrical to globose, usually terminal, each spikelet or spikelet cluster subtended by a deciduous involucre of 1-many bristles, these sometimes in 2 or more series, varying from slender and free to flattened, spiny, and connate at the base. Spikelets narrowly lanceolate to oblong, dorsally compressed, usually glabrous or almost so; lower glumes up to 1/2 the length of the spikelets, sometimes suppressed; upper glumes from very small to equally the lemmas; lower lemma in each spikelet male or sterile, its lemma membranous, varying length but often equaling the upper; upper lemma in each spikelet membranous to coriaceous, its thin margins overlapping much of the palea. Grains oblong and dorsally compressed to subglobose.

Key to the species of Cenchrus s.l. in Somaliland and Somalia.

ADDED NOTES: Traditionally, Cenchrus referred to the species with involucres composed of hard, flattened, and spiny "bristles" that were connate at the base and were painful to walk on in barefeet whereas Pennisetum referred to the species with slender, relatively soft bristles. There are some species, notably Cenchrus ciliare that have been treated under both names. Additional arguments for combining the two came from molecular and developmental studies.  

Global distribution of Cenchrus.