Lepidium densiflorum is a species of flowering plant in the mustard family known by the common names common pepperweed and prairie peppergrass. It is a common and widespread plant in North America, where it grows in many habitats across Canada and the United States. It grows easily in disturbed sites and it is considered a weed in some areas. Lepidium densiflorum is an annual or biennial herb producing a short, erect, branching stem up to about 30 centimeters in height. Leaves grow in a basal rosette at the base of the stem and reach up to about 10 centimeters long; leaves higher up on the stem are smaller and less prominently lobed. The plant produces raceme inflorescences of tiny flowers with sepals each only about a millimeter long. There are usually no petals, though sometimes vestigial petals appear near the sepals. The fruit is a few millimeters long.