Scientific Name: Thlaspi arvense

Common Name: field pennycress

Other Common Names: fan-weed, penny-cress, french-weed, stink-weed, bastard-cress

Habit: Seedlings have spoon-shaped cotyledons 4-10 mm long and 2-6 mm wide with stalks that can reach 7 mm in length. Mature plants reach heights of up to 80 cm tall and have a slender taproot with fibrous secondary roots. Plants are pale-green but turn yellow soon after flowering. This specimen has a strong turnip odor.

Leaves: Field pennycress has smooth, stalkless, oblong leaves, with toothed to smooth margins. Leaves have lobes at the base where they clasp the stem. The egg-shaped leaves of the basal rosette are absent by maturity.

Identifying Characteristics: Round flat notched fruit, small white flowers, and turnip odor.

Flower Seed Head: Appearing April through June flowers are 3-4 mm across with 4 white petals 3-4 mm long. Flowers are found in clusters on the ends of the branches.

Seed Fruit: Fruit is flat and round with a 2 mm notch at the apex. Each fruit has 2 chambers each containing 2-8 seeds. Dark brown seeds with 10-14 circular, granular ridges on each side. Plants may produce as many as 15,000 seeds .

Where Found: Mostly in the northeastern states This plant can be a real problem in row crops, gardens, and other cultivated crops.

  • Life cycle: biennial

  • Milky sap: Not Present

  • Plant type: Herb

  • Thorns: Not Present

  • Plant family: Brassicaceae

  • Leaf arrangement: rosette

  • Leaf shape: lance; oval; round

  • Leaf margin: serrated; wavy; entire

  • Ochrea: Not Present

  • Stem hairs: no hairs

  • Flower color: white

  • Growth habit: upright and nonwoody; prostrate and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: no hairs

  • Root structure: taproot

  • Flower symmetry: radial symetery

  • Flower diameter: pencil

  • Leaf stalk: shorter than leaf