Flower:

Flattish clusters at the top of the plant and the tips of branching stems arising from upper leaf axils. Flowers are about ¼ inch across with 4 white paddle-shaped petals, 6 stamens and a stubby style at the tip of a green ovary.

Alternating with the petals are 4 oval-oblong sepals that are about half as long as the petals, light green with thin, whitish edging. Flower stalks are slender, erect to ascending, hairless.

Leaves and stems:

Leaves are in a basal rosette as well as alternate all along the stem. Basal leaves are long stalked, generally spatula shaped and wilt away early. Lower stem leaves are irregularly toothed or shallowly lobed, 1 to 4 inches long, up to 1½ inches wide, mostly widest above the middle, tapering to a stalk at the base.

Leaves usually become more lance-oblong, less toothy, and stalkless as they ascend the stem, with a pair of lobes (auricles) at the leaf base, and are sometimes clasping. Surfaces are minutely hairy to hairless. Stems are erect, unbranched except in the flower clusters, hairy especially on the lower stem, and usually multiple from the base. Plants form colonies from creeping rhizomes.

Fruit:

Fruit is a somewhat flattened, 2-chambered pod, teardrop to upside-down heart-shaped in outline, widest near the base, up to about 1/6 inch (4mm) long with the remains of the style persisting at the tip. Each chamber contains a single seed. The pod does not split open when mature.

Notes:

White-top has only been recorded twice in Minnesota and not since 1964, though it is a common weed in western North American and in other parts of the Midwest. It is a fairly uniquie species: the flattish clusters of tiny 4-petaled flowers do not elongate much, which readily distinguishes it from other Lepidium species, and it is also a perennial where the others are mostly annuals.