Solanum nigrum

S. nigrum is a very variable ephemeral, annual or sometimes biennial herb, 0.2–1.0 m tall, reproducing only by seed. It has a strong white taproot, with many lateral roots being produced in moist and fertile surface soils.
Stems vary from prostrate to ascending or erect, and from herbaceous in ephemeral plants to rather woody or even shrubby in those that survive long enough to be biennial. Stems are round or angular, smooth or sparsely hairy, and green to purplish.
Leaves are alternate, ovate and are carried on short stalks, 2–8 cm long, and vary between plants from smooth-edged to shallowly lobed. They are opaque, matt and dark green both above and below, and either smooth or finely hairy.
The small, white, star-shaped flowers are carried in umbels on slender stalks developing directly from the stems between the leaves. Each cluster usually carries from 5–10 flowers, which open sequentially over several days. The flowers are 5-8 mm across, and have prominent yellow centres.
Fruits are globular, dark green, matt berries 5–13 mm across, matt black when ripe, which contain many flattened, finely pitted, yellow to dark brown woody seeds approximately 1.5 mm long.
Seedlings of S. nigrum agg. all exhibit epigeal germination. The hypocotyl is commonly slender, about 1 cm long, green or purplish and distinctly hairy. The spreading cotyledons are slender, about 5 mm long, and taper towards the tips. The epicotyl is slender, smooth to finely hairy, and carries small, ovate, juvenile leaves that gradually assume the adult shape and size.