Parasitic on many hosts, especially Lycopersicon, Cannabis, and Nicotiana; stems slender, 1-3 dm, usually with 1 or 2 branches; spikes slender, rather loose and open, the axis often exposed; cal-tube broad, equaling or a little shorter than the 4 equal, caudate- acuminate lobes (a minute fifth lobe rarely developed); cor 12 mm, the tube pale yellow, the limb blue; 2n=24. Native of Europe and w. Asia, rarely intr. in our range, as in Ky.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.