Perennial pepperweed is a native of southern Europe and western Asia and grows 1 to over 3 feet (0.3-0.9 m) tall.
The lanceolateleaves are bright green to gray-green, have a smooth (entire) to toothed margin. The basal leaves are larger than upper leaves.
The white flowers develop in dense clusters near the ends of branches. Individual flowers are very small, but the entire top of the plant blooms in early summer through fall.
Tall whitetop produces a two-seeded fruit capsule. The reddish-brown seeds are round, flat, slightly hairy, and about 1/16 inch (1 mm) long.
Perennial pepperweed grows in waste places, wet areas, ditches, roadsides, and cropland, and is very difficult to control once established. The robust, spreading roots and numerous seeds make this weed difficult to control. Mechanical measures spread the plant and control treatments with chemicals must be timed properly or the effort is wasted.
Leaves and stems are covered with a waxy layer making this perennial difficult to control.
Dense flower clusters appear in early summer on perennial pepperweed.
Owens Valley throughout pastures, canals and ditches and in some isolated spring sites in the Inyo Mountains and into Nevada, north of Bridgeport – Inyo and Mono Counties.