Brown flatsedge (Cyperus fuscus) is widely distributed in Europe, Asia, the Indian subcontinent, and the Mediterranean region of Northern Africa. It was apparently introduced into North America in the late 1800s and has steadily moved southward and westward. Brown flatsedge is reported new to Arkansas and Mississippi herewith. Field observations from early spring until frost were made between 2003 and 2007 from populations present at three sites: Chicot County, Arkansas, and Pearl River and Washington counties, Mississippi. Under natural field conditions, brown flatsedge plants germinated from late March and early April until frost. Inflorescences were observed in mid-May and seed production continued until frost. In field populations, the average numbers of scales per spikelet, inflorescences per plant, and spikelets per inflorescence were 15, 28, and 33, respectively. Greenhouse experiments were established in 2008 at Stoneville, MS, to determine growth parameters and the reproductive potential of brown flatsedge. In greenhouse experiments, by 10 wk after emergence (WAE), brown flatsedge plants were 30.2 cm tall and 63.9 cm in diameter, and dry weights were 1.4, 1.0, 2.0, 0.5, and 1.9 g for roots, culms, leaves, bracts, and inflorescences, respectively. Brown flatsedge culms and inflorescences appeared 5 WAE, and by 9 WAE all plants were producing seed. Brown flatsedge could pose a threat to natural plant communities and rice agriculture in Arkansas, Louisiana, Mississippi, Missouri, Tennessee, and Texas. Additional research is needed to determine seed longevity and ecological range potential, and to develop inexpensive and effective control methods.

Nomenclature: Brown flatsedge, Cyperus fuscus L. CYPFU