Submodule 5: Most Common Western Rangelands Weeds

Purple Loosestrife

Purple loosestrife (Lythrum salicaria) is a perennial forb that can be from 1.5 to 10 ft (0.5 to 3 m) high. Each plant has four to six erect stems that can be branched. Leaves are smooth-edged, from 0.75 to 4 in (2 to 10 cm) long and usually less than 0.5 in (1.3 cm) wide. They are lance-shaped and usually rounded at the base. Stems and leaves are often covered with a downy hair. Roots are thick and woody with a distinct root crown that can be 20 in (50 cm) in diameter; shoots arise from buds on this crown in the spring. Up to 50 stems have been observed to grow from a single crown on mature plants. Flower spikes, usually from a few inches to 3 ft tall (1 m), are made up of numerous florets. These flowers are magenta-colored and very showy. Plants bloom throughout the growing season.

Purple loosestrife (photo courtesy Fish and Wildlife Service)