Aethusa cynapium is an annual herb to 70 cm tall; plant poisonous.
Leaves alternate, 2-3 times pinnate, broadly deltoid, leaf segments narrow, pointed, shiny.
Flowers small, petals white, no sepals; inflorescence of umbrella-shaped clusters to 5 cm wide, “secondary umbels with 3-4 bracts, curved downwards, linear, narrow, sharp-pointed” (NatureGate http://www.luontoportti.com/suomi/ en/kukkakasvit/fools-parsley; 16/12/2013); blooming and fruiting June-Sept.
Fruit dry, broadly egg-shaped, 0.3 x 0.2 cm, prominently ribbed.
Wetland status: NL.
Frequency in NYC: Very infrequent.
Habitat: Open disturbed habitats, gardens.
Notes: Apiaceae of open sites are eaten by larvae of the black swallowtail butterfly, Papilio polyxenes (Papilionidae). (Tallamy 2003; Pyle 1981).