LucasLand

The Wildflowers

Black Mustard

Brassica nigra

From Missouri Plants

Stems - To +75cm tall, erect, herbaceous, single or few from base, glabrous and glaucous above, often pubescent to hirsute near base, branching above, from taproot. Branches erect, staying mostly parallel to main axis.

Leaves - Alternate, petiolate. Petioles winged, to +/-2cm long. Wing 1-2mm broad. Lowest leaves lyrate pinnatifid, to +/-15cm long, 5-6cm broad, glabrous, glaucous. Upper leaves oblong to obovate, entire or with a few coarse shallow teeth, glaucous below, dark green above, glabrous, to +/-6cm long, -2cm broad.

Inflorescence - Terminal racemes elongating in fruit to +60cm. Pedicels 2-4mm long in flower, to 1.3cm long in fruit, glabrous.

Flowers - Petals 4, yellow, clawed, glabrous. Claw to 3mm long. Limb 3-4mm long, +3mm broad. Stamens 6, erect. Filaments greenish-yellow, to -4mm long, glabrous. Anthers yellow, to 1.5mm long. Ovary green, terete, 3mm long, glabrous. Style 1.3mm long, persistent in fruit. Sepals 4, greenish-yellow, -4mm long, 1mm broad, linear, erect to spreading, glabrous, margins often revolute. Siliques to +4.5cm long, terete to 4-angled, with beak to +/-8mm long, glabrous ascending and usually parallel to stem axis. Seeds +20 per fruit, brownish-black.

Flowering - April - November.

Habitat - Fields, waste ground, roadsides, also cultivated.

Origin - Native to Eurasia.

Other info. - For some reason I never got around to scanning in the leaves of this plant. Regardless, the plant can be identified in the field by the massive number of erect fruits it produces, its deep green leaves, and its small yellow flowers. The stems are long and thin. The plant often falls over when it reaches maturity because of the large number of fruits produced.
Like many of the members of this family and genus, the plant is introduced and care should be taken not to spread it in the wild.
B. nigra plant is often grown for its small greens and for its seeds, which are used to make mustard.