field pennycress
Family
BrassicaceaeScientific Name
Thlaspi arvense
Other Common Names:
penny-cress
bastard-cress
french-weed
fan-weed
stink-weed
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.
Growth Habit
Varies:
upright and nonwoody,
prostrate and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
pencil
Dominant Flower Color
white
Flower Symmetry
radial symmetery
Leaf Hairs
no hairs
Leaf Shape
Varies:
round,
lance,
oval
Leaf Arrangement
rosette
Leaf Margin
Varies:
entire,
serrated,
wavy
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
no hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
biennial
Ochrea
not present
Plant Type
Herb