The base of the stems is semi-woody. Upper leaves are sessile, which means the leaves have no stalk and are directly attached to the stem. Perennial pepperweed is a prolific seed producer, capable of producing more than six billion seeds per acre of infestation. Nearly microscopic, reddish-brown seeds occur in an elongated pod and are rounded, flattened and slightly hairy. Enlarged root forms woody crown.
Basal leaves are larger than upper leaves.
Flower is small and white. Dense white flower clusters of six to eight tiny blossoms occur near the ends of stems. Small seed pod with scattered hairs. New plants shoot up from the underground root and enable perennial pepperweed to form dense monocultures that block sunlight from reaching the soil, thus suppressing the growth of other plants. Whitetop is a noxious weed that is usually much shorter than perennial pepperweed and blooms in mid-May.