Taprooted perennial to 1 m, branched above; lvs once-pinnate; lfls 3-9, broadly triangular to suborbicular, usually deeply 3-lobed into cuneate-obovate, serrate or incised segments; umbels sessile or short-pedunculate, the several rays 1-2 cm; proper invol and involucel none, but some of the numerous umbels sometimes sessile and closely subtended by one or more reduced leaves; 2n=22. Native of Eurasia, occasionally escaped in our range, but scarcely persistent. May-July. (Celeri g.)
Three other spp. are merely casual with us. A. leptophyllum (Pers.) F. Muell., of trop. and subtrop. Amer., is an annual with filiform lf-segments. A. repens (Jacq.) Lag. and A. nodiflorum (L.) Lag. are Mediterranean rhizomatous perennials. The former has a well developed involucre, the latter does not.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.