Purple loosestrife (Lythrum salicaria), originally introduced from Eurasia as a garden ornamental in the early 1800s, has escaped cultivation and become an odious weed that can completely take over wetlands and displace all the native species. This perennial, which spreads by rhizomes, often forms dense stands impeding water flow in canals, ditches and streams, reducing wildlife habitat. Eventually purple loosestrife can alter the wetland’s structure. This is one nasty plant, yet naive gardeners continue to utilize purple loosestrife in flower gardens. It is pretty!
Also called purple lythrum. purple loosestrife has an erect, leafy stem that may branch above. The opposite, lance-shaped leaves are pointed, hairy and can be slightly heart shaped at the base. The red-purple flowers are crowded into long, vertical racemes (inflorescence with stalked flowers blooming from the bottom) at the stem tips. The five to seven large petals that form each flower have a crinkly (or wrinkled) appearance. The fruit is a two-chambered capsule with many seeds. A single plant can produce more than two million seeds annually! The plant can grow from one to six feet in height.
There is no effective method of controlling purple loosestrife except where is occurs in small stands that can be intensively managed through uprooting by hand, water level manipulation, herbicides, and mowing or cutting. Unfortunately these methods of control require that all vegetative plant parts be removed and are costly. Eradication by herbicides is non-selective. And no matter what method is used long-term maintenance is required.
Biological control is also being used. Host specific insect species (two leaf eating beetles, one root mining weevil and one flower feeding weevil) are being released in some areas as biological control organisms for purple loosestrife. Thus far the success has been mixed with control, not elimination, of purple loosestrife in most cases.
Prevention and early detection of infestations perhaps are the best control methods for stopping purple loosestrife’s damage.
The common name “loosestrife” comes from “lysimachia” and means to “release from strife” or agitation. Loosestrife seems to have some effect in repelling flies and gnats. When placed upon the yokes of oxen or other working animals purple loosestrife was supposed to calm the animals.
These purple loosestrife plants were photographed along the Tule River (Shasta County CA).
Purple loosestrife – a beautiful flower but a huge environmental problem.