Perennial; stems clustered, 4-10 dm, roundly 4-angled, usually finely puberulent; lvs in whorls of 8-12, ±linear, 1-nerved, 1.5-4 cm נ0.5-3 mm, acute, shining and usually hairy above, densely puberulent beneath, the margins usually ±inrolled; fls bright yellow, forming a dense, showy cymose panicle; 2n=22, 44. Native of Eurasia, now a weed of roadsides and fields in our range, especially northward. June-Sept. (A strictly diploid phase with odorless, lemon-yellow fls and open ±interrupted infl, has been called G. wirtgenii F. W. Schultz (G. verum ssp. wirtgenii), in contrast to typical G. verum, diploid or tetraploid, with fragrant golden-yellow fls and denser infl. We have both.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.