Our only specimen of this species was collected by the late Carl Buhl in an old tamarack bog about 7 miles west of La Porte, La Porte County. Since it is reported from both Illinois and Michigan, it is doubtless more or less frequent in the dune area.
Resembling no. 3 and often mistaken for it; infl-tips nodding; hypanthium 1.5-4 cm; sep 1-2 cm, the free tips 1-3 mm, subterminal, the actual end of the sep represented by a distinct transverse ridge or a small lobe; pet 1-2 cm; anthers 4-7 mm; style 0.5-2.5 cm; fr 1.5-4 cm, only slightly tapering; seeds 1.8-2.2 mm; 2n=14, a complex heterozygote. Disturbed open places, abundant especially northward; Nf. to Va. and W.Va., w. to Minn. and Ark. July-Oct. Highly variable. Closely and minutely canescent-strigulose plants, without gland-tipped hairs, occur mainly from Mass. to Va. and have been called var. oakesiana (Robbins) Fernald (O. oakesiana), in contrast to var. parviflora, widespread but more common northward, with intermingled long and short hairs, often some of them gland-tipped, varying to nearly glabrous. (O. angustissima; O. cruciata)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.