This is well-known (e.g. FNA 24, D, Y, W) in some midwestern regions (from Minn. to Tex.) and in southeastern coastal states (Miss. to Pa.). It is locally abundant in open woodlands on base-rich soils. F. paradoxa is much less frequent across most of the Ohio Valley, but there are apparently native plants on the Mississippian Embayment and old river terraces of s. Ill., sw. Ind. and w. Ky. Uncertain records mapped here may be based adventive plants, or perhaps transitional to robust open-grown subverticillata. However, Aiken & Lefkovitch (1993) showed that these two species are generally distinct, with inconclusive evidence of hybridization. [A similar situation occurs in Sphenopholis obtusata versus S. intermedia.] Based on W's review, paradoxa differs mostly clearly in its principal lowermost panicle branches with 8-20 spikelets clustered near the end (versus 2-7 spikelets scattered along the distal half); spikelets are broadly ovate, ca. 4-6 mm wide (versus narrowly ovate, ca. 2-4 mm wide). Instead, FNA 24 emphasized its more ascending inflorescence branches, more imbricate spilkelets, and larger upper glumes (mostly 4-5 mm versus 3-4 mm).