Purple loosestrife Lythrum salicaria
Purple loosestrife is a native of Europe and Asia that was first introduced into the U.S. in the 1800s for its ornamental and medicinal value. The plant adapts well to a wide variety of wetland conditions, and blooms from June until September. This long blooming season enables it to produce large numbers of seeds.
Distribution in Utah: Small, isolated communities exist throughout the state. Since its introduction to America, purple loosestrife has spread, according to the U.S. Fish and Wildlife Service, to every state except Florida.
Identification: Flowers have five or six purple petals surrounding small, yellow centers. Individual flowers make up each flower spike. Leaves have smooth, downy edges, and are arranged in alternating pairs, but they may appear in groups of three. Mature plants are three to six feet tall.
Problem: Purple Loosestrife is a hardy perennial wetland plant introduced from Europe. The plant invades marshes, lake shores and ditch banks, replacing cattails and other native wetland plants by forming dense stands that have relatively little value as wildlife cover, food or nesting habitat.
Means of spreading: Seeds disperse from gardens and nurseries into wetlands, lakes and rivers. Once introduced, seeds are easily spread via water or wildlife. The plants also spreads via underground stems. Sprouts from these stems form dense homogenous stands of purple loosestrife that choke out native plants. Humans also spread seeds through equipment, clothes or through intentional decorative propagation.
Management and containment: Plants can be destroyed by hand or through chemical herbicides. Recently, U.S. biologists have had some success in controlling purple loosestrife by introducing insects from its native Europe and Asia that naturally feed upon the plant.