Wild mustard

Sinapis arvensis L.

Life cycle

Erect winter or summer annual.

wild mustard rosette
Wild mustard rosette.

Leaves

Seedlings have smooth, kidney-shaped cotyledons and prominently veined, bristly hairy leaves that initially develop from a basal rosette. Lower leaves are irregularly lobed and toothed with petioles; upper leaves are alternate, stalkless to short-stalked with coarsely toothed margins and pointed tips, gradually becoming smaller toward the top.

wild mustard lower leaf wild mustard cotyledon
Wild mustard lower leaf (left). Kidney-shaped cotyledons of wild mustard (right).

Stems

Erect, up to 3-foot-tall stems bolt from a basal rosette to flower. Stems are bristly hairy at the base, often branched and nearly hairless at the top.

wild mustard stem
Wild mustard stem.

Flowers and fruit

Bright yellow flowers with four petals are found in terminal clusters. Fruit are 1- to 2-inch-long, cylinder-shaped capsules with a four-angled beak at the tip that contain round, black to purple seeds.

wild mustard flower wild mustard fruit
Wild mustard flower (left) and fruit (right).

Reproduction

Seeds.

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