Sisymbrium altissimum is an annual herb or winter annual, to 1 m tall, from a rosette, stems much branched above.
Leaves alternate, early or overwintering rosette leaves with wide-based regular segments, stem leaves pinnately divided with 5-8 long, lobes linear to narrow, toothed or entire, upper leaves smaller with fewer, filament-like lobes.
Flowers pale yellow, 4 petals, to 0.8 cm long, blooming at the top of a raceme with developing fruit below, self fertile (autogamous), (Mulligan and Kevan 1973); blooming June-Sept.
Fruit dry, capsule, to 1 cm long, 0.1 cm wide.
Wetland status: FACU-.
Frequency in NYC: Very infrequent.
Habitat: Open areas. Agricultural weed.
Notes: Sisymbrium species are host to the larvae of the falcate orangetip butterfly, Anthocharis midea (Pieridae).