This occurs on dry acid soils in grasslands of southeastern states, especially on the Coastal Plain; it is rare to absent in the Ohio Valley. See notes under aciculare; the aciculare group (Sect. Angustifolia) contains several intergrading species or subspecies. Also, there are occasional hybrids with diploids in other groups (FNA 25). D. angustifolium is distinguished from typical aciculare as follows (W; Ladd & Thomas 2015): longest vernal blades to 16 cm (versus 6 cm), widest vernal leaf blades 4-8 mm, usually longitudinally wrinkled (versus 2-5 mm wide, not noticeably wrinkled);; vernal and autumnal spikelets 2.2-3.1 mm long (versus 1.5-2.3 mm); autumnal leaf blades flat (versus involute), the larger up to 9 cm by 2-4 mm (versus 3 cm by 1 mm).