Artemisia biennis is naturalized and weedy in the eastern portion of its range. It is morphologically similar to A. annua, differing primarily in the coarser leaf lobes and larger heads that are sessile in axils of leaflike bracts. Artemisia biennis is considered native to the northwest United States; it may be introduced in other parts of its range. The type specimen is a horticultural specimen from New Zealand.
Coarse, nearly inodorous, glabrous annual or biennial 3-30 dm; lvs 5-15 cm, pinnatisect nearly to the midrib into several narrow lobes that are usually again sharply toothed, or the lower bipinnatifid; infl dense, spike-like or of spiciform branches, the heads usually numerous, crowded, scarcely pedunculate; invol glabrous, 2-3 mm; achenes ellipsoid, 4-5-nerved; 2n=18. Waste places and stream-banks, especially in sandy soil; native to nw. U.S. but widely distributed in our range and elsewhere as a weed. Aug.-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.