Lythrum salicaria (aquatic plant, herb)

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Taxonomic name: Lythrum salicaria (Linnaeus 1753) Synonyms: Lythrum salicaria var. gracilior Turcz., Lythrum salicaria var. tomentosum (P. Mill.) DC., Lythrum salicaria var. vulgare DC. Common names: Blutweiderich (German), purple loosestrife (English), rainbow weed (English), salicaire (French), spiked loosestrife (English) Organism type: aquatic plant, herb Lythrum salicaria is an erect perennial herb with a woody stem and whirled leaves. It has the ability to reproduce prolifically by both seed dispersal and vegetative propagation. Any sunny or partly shaded wetland is vulnerable to L. salicaria invasion, but disturbed areas with exposed soil accelerate the process by providing ideal conditions for seed germination. Description Lythrum salicaria is an erect, perennial herb with a woody four-sided stem and whorled leaves. Plants are usually covered by a soft down. Leaves are generally opposite, lance-shaped but heart-shaped or rounded at the base. Mature plants can have 30 to 50 stems emerging from a single rootstock and produce as many as 3 millions seeds annually. L. salicaria can grow from 1.2 to 3m high, depending upon conditions. Showy, trimorphic, magenta-coloured flowers, with five to seven petals, are produced throughout most of the summer. Woody stems of plants remain standing during the winter, when the plant is readily identified by its brownish colour and spiral-shaped capsule clusters. Similar Species Liatris spp., Epilobium angustifolium, Lythrum alatum, Spiraea douglasii, Verbena hastata More Occurs in: riparian zones, ruderal/disturbed, wetlands Habitat description Lythrum salicaria is capable of invading a variety of wetland habitats, including marshes, river and stream banks, pond edges, lakes, road site ditches, and reservoirs. The plant prefers moist soil with neutral to slightly acidic pH. Once established, however, L. salicaria can exist in a wide range of soil types. Disturbed areas are more prone to invasion because exposed soil is ideal for germination. General impacts As Lythrum salicaria establishes itself, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality food source and habitat for wildlife. Lythrum stands can deleteriously impact wildlife habitat used by birds and furbearers. L. salicaria forms dense homogeneous stands that restrict native wetland plant species, including some endangered plants. L. salicaria can overrun wetlands and almost entirely eliminate open water habitat if left untreated. The recreational and aesthetic value of wetlands and waterways is diminished as dense stands of L. salicaria choke waterways and decrease biodiversity. Uses Lythrum salicaria is grown for medicinal uses and planted by beekeepers for its nectar-producing capabilities. It has been used as a herb for diarrhea, dysentery and dried leaves were used to heal wounds, ulcers and sores. L. salicaria is also widely sold as an ornamental in states where regulations do not prohibit its sale and distribution. Geographical range Native range: Lythrum salicaria is native to Europe (extending from Great Britain to central Russia), Japan, Manchuria China, southeastern Asia, and northern India. Known introduced range: It has invaded Canada, the United States, Ethiopia, Australia. Introduction pathways to new locations Floating vegetation/debris: Landscape/fauna "improvement": Local dispersal methods Garden escape/garden waste: Water currents: Management information Preventative measures: The best control measure, however, as with many invasive plants, is to preserve a healthy native ecosystem to prevent or slow invasion. Physical: Small infestations (< 100 plants) of L. salicaria can be controlled but cutting and pulling. Cutting should be done just before the plants begin flowering to avoid spreading seed. Pulling should be done by carefully removing all root fragments and disposing of all uprooted plants. Plant materials should be dried and burnt where possible. These fragments and uprooted plants could grow into new plants, possibly making the problem worse. Mowing and burning is ineffective and sometimes makes the problem worse. Chemical: Herbicides are most commonly used for quick, effective control of L. salicaria. Spot treating with a glyphosate type herbicide (e.g., Rodeo for wetlands, Roundup for uplands) is effective on older plants. These herbicides may be most effective when applied, as plants are preparing for dormancy, however, mid-summer and late season treatments may be needed to reduce the amount of seed produced. In Canada, only Roundup is registered for the control of Lythrum in terrestrial areas only. Multiple chemical treatments are usually required as new seedlings annually emerge from the seed bank. Chemical treatments may not be desired in sensitive wetland habitats. Biological: Although these mechanical and chemical control measures are effective on small populations, biological controls are needed for long-term control of larger populations. In the North American region four insects from Europe have been approved by the U.S. Department of Agriculture for use as biological control agents: the root-mining weevil (Hylobius transversovittatus ) and two leaf-feeding beetles (Galerucella calmariensis and Galerucella pusilla ) and Nanophyes marmoratus a herbivorous weevil. Galerucella calmariensis , G. pusilla and H. transversovittatus have been released across the United States and Canada. In many release sites Galerucella calmariensis has provided successful control of the target weed in as little as 3 years reducing plant populations by as much as 100%. The impact of these introduced beetles on native, non-target species is considered low. Reproduction Lythrum salicaria reproduces by seed and vegetatively. Flowers require pollination by insects and seeds require open, wet soils and a high temperature to germinate. Flowers are tristylous and pollination restricted to crosses between the style of one length with stamens of the corresponding length. L. salicaria can also spread vegetatively by leftover pieces of trampled, clipped, mowed and pulled plants. A mature plant over 2mtrs tall can have as many as thirty flowering stems and produce two to three million seeds per year. Seed production is dependent upon age, size and habitat conditions. Seeds are very small and are transported by wind, water, wildlife, vehicles, construction equipment, and humans. Seed survival can be as high as 70%, creating an extensive seed bank. Seedling establishment occurs in late spring and early summer or after soil disturbances including chemical applications. Shoots from vegetative reproduction grow at a rate of approximately 0.3mt per year. Lifecycle stages Seeds can remain viable in the soil for many years and those submerged in water can remain viable for about 20 months. This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress Cory Lindgren, Provincial Coordinator Manitoba Purple Loosestrife Project (MPLP) Oak Hammock Marsh Manitoba Canada Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) To contribute information, please contact Shyama Pagad. Last Modified: Wednesday, 22 February 2006