Erect, branching, glandular-hairy annual 1-3 dm; lvs linear, 1-2 cm, obtuse, narrowed below but scarcely petiolate; pedicels 10-15 mm, arising from many or most axils; sep linear-spatulate, unequal, 3 mm; cor 5-6 mm, blue-purple, with yellow on the palate, the spur 1.5-2 mm; fr subglobose, 5 mm; 2n=14, 28. Native of Europe, now widely established in waste places, especially on cinder railway-ballast, throughout our range. June-Sept. (Linaria m.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
This species is reported to have been introduced in 1874 at Camden, New Jersey. Since that time it has spread extensively and is always found in cinder or sand ballast along railroads. I first found it in Vigo County in 1918. I have seen it spread from a few plants along the traction line in Wells County until the railroad bed for miles in flowering season is blue with it.