Chrysanthemum parthenium

Perennial from a taproot or stout caudex; stem 3-8 dm, puberulent above; lvs mainly cauline, finely hairy at least beneath, pinnatifid, with incised or again pinnate, rounded segments, evidently petiolate, the blade to 8 נ6 cm; heads several or many in a corymbiform infl, relatively small, the disk 5-9 mm wide; rays 10-21, or more numerous in double forms, 4-8 mm, white; achenes subterete, ca 7-10-ribbed; 2n=18. Waste places; native of Europe, occasionally intr. or escaped in our range. June-Sept. Generic position uncertain. (Matricaria p.; Tanacetum p.)

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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