Rhizomatous perennial, glabrous throughout, or occasionally hairy; stems erect or ascending, 1-4 dm; lvs all opposite, sessile, linear to lanceolate, 2-8 cm נ2-15 mm, (3-)4-20 times as long as wide, entire or with a few remote, divergent, slender small teeth; racemes axillary, pedunculate, mostly 5-20-fld, the pedicels becoming 6-17 mm; cor bluish, 6-10 mm wide; fr flattened, 2.5-4 mm, evidently wider than high, conspicuously and rather broadly notched; style 2-4 mm; seeds 5-9 per locule, 1.2-1.8 mm; 2n=18. Swamps and bogs; Eurasia and the n. two- thirds of the temperate zone in N. Amer., blanketing our range. May-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Infrequent to frequent in the lake area with two stations south of it. It prefers the dried-up borders of ponds that are well covered with old leaves. While it sometimes grows in marshes and in muck it prefers to root in decaying vegetation.