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*The following is based on Gann, G.D., K.A. Bradley & S.W. Woodmansee. 2002. Rare Plants of South Florida: Their History, Conservation, and Restoration. The Institute for Regional Conservation: Miami. For updated species accounts, see Citation below. For the original text, follow the link in the Update field. If no Update field is displayed, then cite as the original publication.

Cenchrus brownii Roem.

Slimbristle sandbur

South Florida Status: Extirpated. Last native population vouchered in 1954 on the island of Key West.

Taxonomy: Monocotyledon; Poaceae.

Habit: Annual terrestrial herb.

Distribution: Native to South Florida, the West Indies, Mexico, Central America, and South America. Introduced and naturalized in the Old World.

South Florida Distribution: Native to the Monroe County Keys. Apparently briefly naturalized in Miami-Dade County.

South Florida Habitats: Native to dry sandy soil on the margins of hammocks, probably on dry, open, coastal berms. Most collections are from dry, disturbed sites.

Protection Status: Not listed by any agency.

Aids to Identification: Hitchcock & Chase (1950) has an illustration. The spikelets of C. brownii most resemble those of C. echinatus. The burs of C. brownii are narrower (2.7-4.2 mm wide vs. 4-5.3 mm wide), and shorter (4-5.3 mm long vs. 5.3-8 mm long excluding spines) than those of C. echinatus (Wunderlin, 1998).

References: Chase, 1920; Small, 1933a; Hitchcock & Chase, 1950; DeLisle, 1963; Long & Lakela, 1976; Hall, 1978; Correll & Correll, 1982; Wunderlin, 1998.

Synonyms: C. viridis Spreng.

Historical Context: Ferdinand Rugel first collected slimbristle sandbur in 1846 on the island of Key West (120, US). It was not vouchered there again until 1954, when Ellsworth P. Killip collected it in a lawn along South Street (44292, US). This appears to be the last collection of slimbristle sandbur within its natural range in South Florida. Several other collections are known from the Florida Keys. Charles L. Pollard made one collection in 1898 on Upper Matecumbe Key (145, NY, US). In 1902, Albert S. Hitchcock made the first collection on Key Largo (Chase, 1920). Agnes Chase made another collection in 1907 near the village of Planter (3931, US). Chase’s label stated “Erect or nearly in a hole in coral rock, cleared spot in brush land.” Harold N. Moldenke collected it a third time on Key Largo in 1930 “in dry sandy soil at edge of hammock” (781, NY).

Olga Lakela collected one additional specimen in 1963, from a disturbed road edge in southern Miami-Dade County (26159, US). This appears to have been a short-lived, probably introduced population. Slimbristle sandbur has been reported for Biscayne National Park (Stalter et al., 1999), but there are no specimens to corroborate this report.

Comments: Due to the fact that slimbristle sandbur is an introduced weed in the Old World and is mostly known from disturbed sites in South Florida, extreme caution should be exercised before proceeding with any reintroductions.

Recommendations: · Consider reintroduction to Key Largo at Crocodile Lake National Wildlife Refuge, Dagny Johnson Key Largo Hammocks Botanical State Park, and Dove Creek Hammocks. · Review for listing by FDACS and FNAI.