[ click on any image below to see larger version ]
Family: Brassicaceae (Mustard family)
Mid-Atlantic bloom time: April - June
Common Winter Cress' bright yellow flowers have a characteristic boxy 4-petal form.
According to Wikipedia,
"The genus name Barbarea derives from Saint Barbara, the patron saint of artillerymen and miners, as this plant in the past was used to soothe the wounds caused by explosions."