Alternate name: Common Winter Cress
Family: Brassicaceae, Mustard view all from this family
Description This is the only yellow-flowered mustard with completely smooth pinnately lobed leaves and long, cylindrical fruit with short terminal beaks.
Habit: introduced annual, biennial or perennial herb; erect, smooth, ridged stems branched above; taprooted.
Height: 6-48 in (0.15-1.2 m)
Leaf: in basal rosette, dark green, smooth, shiny, lyrate, usually pinnately divided into 3-9 lobes, edges sometimes toothed or wavy, 1-8 in (25-200 mm) long including stalk; on stem, alternate, becoming smaller, less lobed, oval or circular, clasping or stalkless, swollen at the base.
Flower: small, with 4 pale yellow spatulate petals on thin stalk, to 0.25-0.5 in (6-12 mm) wide; held in dense rounded terminal cluster above the foliage.
Fruit: long, thin, cylindrical pod, beaked, linear to curved, 0.3-1.5 in (7-38 mm) long, to 0.1 in (2 mm) diameter; held upright on short thin stalk.
Warning Toxic to animals if ingested in large quantities. Humans should generally avoid ingesting plants that are toxic to animals.
Flower April through October.
Habitat Moist sites: wet meadows, streambanks, alluvial bars, roadsides, cultivated fields, fallow fields, waste places, ditches, damp grasslands, disturbed sites, lawns; to 10,000 ft (3000 m).
Range Native to Europe; introduced to North America in cargo or ballast in the early 1800s; now naturalized throughout the continent, except Alaska, northern Canada, Nevada, Arizona, Texas, Louisiana, and Alabama.
Discussion Also known as yellow rocket, winter cress, cress, cressy-greens. Considered weedy or invasive in some areas; primarily an agricultural weed.