Lepidium ruderale L.
Family: Brassicaceae
fetid peppergrass, roadside pepper-weed, stinking pepper-weed
[Lepidium texanum Buckley]
Lepidium ruderale image
from USDA Plants website  
Etymology: Lepidium: from the Greek lepidion, meaning "a little scale," in reference to the shape of the fruit pods
Plants: annual/biennial, 8"-20" tall forb, foul smelling
Leaves: lower leaves usually twice pinnately-lobed; upper leaves not clasping
Flowers: 4-parted
Fruits: ovate to elliptic, flat pod, notched at tip, wingless
Habitat: disturbed areas
Conservation Status: Introduced - adventive