This rhizomatous perennial has been spreading into east-central states during recent decades. Though often considered to have originated from East Asia, the species may also be native to warmer regions of southeastern states (FNA 23, Y, W). In Ky. there are widely scattered records from roadside ditches, damp lawns and similar disturbed sites, especially on sandy or gravelly soils; it may be less common on calcareous soils. Mears (1999) has provided most of these records, from his excellent cyperaceous touring in the 1990s; see also Mears & Libby (1995). In addition to having mat-forming rhizomes, gracillima differs from pumila as follows: spikes solitary (versus 1-3); floral scales pale greenish to reddish brown (versus transparent to pale brownish); anthers 0.8-1.1 mm (versus 0.2-0.4 mm); style 1.8-2.2 mm (versus 0.5-0.8 mm); achenes 1.5-1.8 x 0.8-1 mm (versus 1-1.4 x 0.5-0.7 mm).