Perennial, 3-8 dm, colonial by creeping roots; lvs very numerous, pale green, 2-5 cm נ2-4 mm, narrowed below to a petiole-like base; fls numerous in a compact spike, yellow with orange palate, 2-3.5 cm, including the spur; fr round-ovoid, 8-12 mm; seeds winged; 2n=12. Native of Europe, established in fields, roadsides, and waste places throughout temperate N. Amer. May-Sept. (L. linaria)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.