Wild mustard

Sinapis arvensis L. Brassicaceae (Mustard family)

Life cycle

Erect winter or summer annual.


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, and gradually become smaller toward the top.

wild mustard lower leaf wild mustard rosette wild mustard kidney-shaped cotyledons
Wild mustard lower leaf (left), rosette (middle), and kidney-shaped cotyledons (right).


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 base
Wild mustard stem base.

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).



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