Coarse, erect annual to 2 m; stems hexagonal; lvs mostly or all whorled or opposite, lanceolate to lance-ovate, acuminate, sharply serrate; racemes ascending on long peduncles, few-fld; fls purple or blue, varying to white, 3 cm; 2n=18, 20. Native of the Himalayan region, becoming established as an escape from cult. in the ne. part of our range. Summer. (I. roylei)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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