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.
Duration: Annual Nativity: Non-Native Lifeform: Forb/Herb General: Exotic annual, erect to spreading stems 30 cm, rather coarse, grooved. Leaves: Pinnately 3 or 4 times divided into linear-filiform segments, 3-8 cm. Flowers: Petals 0.3-0.4 mm, white, often fading pink. Fruits: Broadly ellipsoid to globose, 1.5-2 mm, mericarps each with 5 prominent narrow ribs. Ecology: Widespread weed, thrives in lawns, where it becomes knotty or spreading. Notes: Very widespread weed, thought to be from Brazil. Ethnobotany: Some in this genus (and old genus Apium) used for flavoring, for tuberculosis, and as potherb. Etymology: Cyclospermum from Greek kyklos, circle or ring and sperma, seed, referring to the shape of the fruit and seeds. Synonyms: Apium leptophyllum, Apium tenuifolium, Cyclospermum ammi Editor: SBuckley, 2010