Gramineae (Poaceae), the Grass Family
Missiongrass is an annual or short-lived perennial species that is polymorphic (variable in appearance), but generally upright and tufted in form. Clumps arise from a hard, knotty base, with erect, branching stems up to 6 feet high. The leaf sheaths are hairless, but have ciliate margins. The linear-shaped leaf blades, which measure 1/6 to 3/4 inch wide and up to 22 inches long, may be hairless or pubescent toward the base. The ligule (intersection of the leaf sheath and leaf blade) is a ciliate membrane. The inflorescences are erect to slightly drooping, terminal panicles to 14 inches long. The inflorescence branches are very short, and the flower spikelets are sessile (stalkless) and densely packed, giving the panicles a spike-like appearance. Inflorescence color is variable, ranging from white, yellow or light brown to pink or purple. Spikelets consist of one fertile floret and one sterile or staminate (male) basal floret. Each spikelet is surrounding by an involucre of plumose (feathery) bristles, with one or several bristles noticeably longer than the others. Upon maturity, the seeds are shed with their bristly involucres, which aid in dispersal.
Native to tropical Africa, missiongrass is now naturalized in tropical, subtropical and warm temperate regions worldwide. It is most frequently found on dry, disturbed sites, including pastures, croplands and roadsides, but has also been documented to invade undisturbed grasslands and open woodlands in Australia. It is particularly common on cleared forest lands in Southeast Asia and the Pacific Islands. In the United States, it has been found only in Florida and Hawaii.
Missiongrass has been vouchered with herbarium specimens from only a few isolated occurrences except in Collier County, where missiongrass seems to be locally established in the Immokalee area. It has been found in a variety of disturbed sites, including roadsides, agricultural fields and levees.
There are three other species of Pennisetum in Florida that have elongated, plumose bristles surrounding the spikelet: kyasumagrass (Pennisetum pedicellatum), elephantgrass or napiergrass (Pennisetum purpureum) and fountaingrass (Pennisetum setaceum). Missiongrass is most reliably distinguished by its shorter (less than 1/6 inch), sessile spikelets.
Missiongrass produces abundant seed, which is dispersed by both wind and water and by attaching to animals, clothing and vehicles. It may also be spread as a contaminant in hay and grain. Branches may also root at the nodes, facilitating vegetative dispersal.
Missiongrass was introduced to many areas as an ornamental and pasture grass. The date and circumstances of its introduction to Florida are not known. This species has a negative impact on the productivity of agricultural fields and pastures and can out-compete and displace native grasses. It also alters fire regimes, resulting in extremely hot fires that can kill native plant species. Missiongrass is a host for maize streak virus. Recent research indicates that Pennisetum, Cenchrus and Odontelytrum form a single group, and Pennisetum and Odontelytrum should be transferred into Cenchrus. Consequently, the accepted name is now Cenchrus polystachios, although this has yet to be changed in the federal or Florida noxious weed lists.
Chemisquy, M.A., L.M. Giussani, M.A. Scataglini, E.A. Kellogg and O. Morrone. 2010. Phylogenetic studies favor the unification of Pennisetum, Cenchrus and Odontelytrum (Poaceae): a combined nuclear, plastid and morphological analysis, and nomenclatural combinations in Cenchrus. Annals of Botany 106: 107-130.