Lythrum salicaria (purple loosestrife)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Soil Tolerances
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Plant Trade
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Lythrum salicaria L.
Preferred Common Name
- purple loosestrife
Other Scientific Names
- Lythrum argyi H.Lév.
- Lythrum intermedium Ledeb. ex Colla
- Lythrum salicaria var. gracilior Turcz.
- Lythrum salicaria var. mairei H.Lév.
- Lythrum salicaria var. tomentosum (P. Mill) DC.
- Lythrum salicaria var. vulgare DC.
International Common Names
- English: purple lythrum; spiked loosestrife
- Spanish: lysimaquia roja; salicaria
- French: salicaire commune
- Portuguese: abre-o-sol; erva-da-vida; quebra-arado; salgueirinha; vassourinha
Local Common Names
- Canada: purple willowherb; salicaire; swamp loosestrife
- Germany: Blut- Weiderich; Gemainer Blutweiderich; Gemeiner Blutweiderich
- Italy: riparella
- Japan: ezomisohagi
- Netherlands: Kattestaart
- Sweden: fackelblomster
- Turkey: tibbi hevhulma
- USA: rainbow weed
- LYTSA (Lythrum salicaria)
Summary of InvasivenessTop of page
L. salicaria, an Old World native, is a highly invasive species of wetlands in North America, beginning to spread rapidly about 140 years after its accidental introduction around 1800. It is a very variable species with an ability to occupy numerous habitats and substrates with the exception of dry places. Its spread and persistence in ecosystems is supported by very high seed production, a vigorous and persistent root system and rapid growth. It is an invasive species and/or noxious weed in almost all states and provinces of Canada and the USA where it is a serious threat to many sensitive wetland ecosystems.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Myrtales
- Family: Lythraceae
- Genus: Lythrum
- Species: Lythrum salicaria
Notes on Taxonomy and NomenclatureTop of page
L. salicaria is a morphologically variable species, with subspecies sometimes distinguished based mostly on pubescence and origin. With hairy to pubescent leaves, subsp. salicaria is very common in temperate areas and submediterranean and subatlantic Eurasia; the glabrous subsp. intermedium is found from eastern Europe to China and Japan; and the tomentose subsp. tometosum dominates in warmer, Mediterranean regions (Wangerin and Schröter, 1937; Dostál, 1989).
DescriptionTop of page
L. salicaria is a perennial herb 30-200 cm tall with a persistent woody rootstock. In North America and exceptionally in the southern limits of its native range, taller plants (up to 350 cm) can be found. Stems are erect and quadrangular in section with evenly spaced nodes in opposite pairs or in whorls of three. Leaves are 3-10 cm long, sessile, lanceolate to ovate and arising from each node (Thompson et al., 1987; Mal et al., 1992). The stem can be without lateral branches but plants usually form branches in the mid to lower part of the stem (Hegi, 1925). The length and number of lateral branches is variable, depending upon environmental conditions, probably soil nutrient status. Leaves are glabrous to pubescent on the stem and branches, or sub-tomentose on the inflorescence. Inflorescences are purple, in a dense terminal spike up to 1m long. In the first year or under poor nutrient conditions, plants usually have one shoot only, which dies at the end of growing season. In older plants, herbaceous stalks with lateral branches, each with terminal spike of flowers, arise from the rootstock to make a wide-topped crown (Thompson et al., 1987). Fruits are oblong-ovoid capsules (3-4 mm long) with two valves. Seeds are very small (200-400 µm in size, 0.5-0.6 mg in mass), thin-walled with two cotyledons and no endosperm (Thompson et al., 1987). The species is heterostylous with three distinct arrangements of pistils and stamens. The flowers are categorized according to stylar morphs as short-, medium- and long-styled (Mal et al., 1992).
Plant TypeTop of page Broadleaved
DistributionTop of page
In its native range, L. salicaria grows in the whole of Europe except high mountainous areas and the most northerly latitudes such as the Faroe Islands, Iceland and northern parts of Scotland, Scandinavia and Russia, with the absolute northern limit being 69°30'N in Norway (Wangerin and Schröter, 1937). The general northern limit is 57°N in the UK, 64°N in Norway, 67°N in Finland, 65°N in European Russia and 61°N in Asian Russia, dropping to 55°N at 97°E and 50°N at Altai, China, near to the Mongolian and Russian borders. The southern limit is 24°N in China and 33°N in Afghanistan and Iran, in dispersed populations. In southern Europe, L. salicaria is common in all countries though is not present in the Balearic Islands and Crete. In Australia, it occurs between 23°S and 42°S and 137°E and 153°E (Wangerin and Schröter, 1937), although distribution data for Australia in USDA-ARS (2007) does not entirely concur with that from Royal Botanic Gardens Sydney (2007). As an exotic species in North America L. salicaria is most common in north-eastern USA and south-eastern Canada (Ontario and Quebec), with a northern limit of 51°N (Mal et al., 1992) and only scattered occurrences up to 56°20'N. In Canada, it is present in all provinces except Yukon and Northwest Territories. In South America, it has only been recorded in Rio Negro, Argentina as an introduced exotic (Wangerin and Schröter, 1937).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Afghanistan||Present||Native||Wangerin and Schr÷ter, 1937|
|China||Present||Present based on regional distribution.|
|-Anhui||Present||Native||Flora of China Editorial Committee, 2007|
|-Fujian||Present||Native||Flora of China Editorial Committee, 2007|
|-Gansu||Present||Native||Flora of China Editorial Committee, 2007|
|-Guangdong||Present||Native||Flora of China Editorial Committee, 2007|
|-Guangxi||Present||Native||Flora of China Editorial Committee, 2007|
|-Guizhou||Present||Native||Flora of China Editorial Committee, 2007|
|-Hainan||Present||Native||Flora of China Editorial Committee, 2007|
|-Hebei||Present||Native||Flora of China Editorial Committee, 2007|
|-Heilongjiang||Present||Native||Flora of China Editorial Committee, 2007|
|-Henan||Present||Native||Flora of China Editorial Committee, 2007|
|-Hong Kong||Present||Native||Flora of China Editorial Committee, 2007|
|-Hubei||Present||Native||Flora of China Editorial Committee, 2007|
|-Hunan||Present||Native||Flora of China Editorial Committee, 2007|
|-Jiangsu||Present||Native||Flora of China Editorial Committee, 2007|
|-Jiangxi||Present||Native||Flora of China Editorial Committee, 2007|
|-Jilin||Present||Native||Flora of China Editorial Committee, 2007|
|-Liaoning||Present||Native||Flora of China Editorial Committee, 2007|
|-Macau||Present||Native||Flora of China Editorial Committee, 2007|
|-Nei Menggu||Present||Native||Flora of China Editorial Committee, 2007|
|-Ningxia||Present||Native||Flora of China Editorial Committee, 2007|
|-Qinghai||Present||Native||Flora of China Editorial Committee, 2007|
|-Shaanxi||Present||Native||Flora of China Editorial Committee, 2007|
|-Shandong||Present||Native||Flora of China Editorial Committee, 2007|
|-Shanxi||Present||Native||Flora of China Editorial Committee, 2007|
|-Sichuan||Present||Native||Flora of China Editorial Committee, 2007|
|-Tibet||Present||Native||Flora of China Editorial Committee, 2007|
|-Xinjiang||Present||Native||Flora of China Editorial Committee, 2007|
|-Yunnan||Present||Native||Flora of China Editorial Committee, 2007|
|-Zhejiang||Present||Native||Flora of China Editorial Committee, 2007|
|Georgia (Republic of)||Present||Native||USDA-ARS, 2007|
|India||Present||Native||Wangerin and Schr÷ter, 1937|
|Iran||Present||Native||Mal et al., 1992|
|Japan||Present||Native||Wangerin and Schr÷ter, 1937|
|Lebanon||Present||Native||Mal et al., 1992|
|Mongolia||Present||Native||Wangerin and Schr÷ter, 1937|
|Pakistan||Present||Native||Mal et al., 1992|
|Syria||Present||Native||Mal et al., 1992|
|Turkey||Present||Native||Wangerin and Schr÷ter, 1937|
|Algeria||Present||Native||Wangerin and Schr÷ter, 1937; Mal et al., 1992|
|Ethiopia||Present||Native||Mal et al., 1992|
|Morocco||Present||Native||Wangerin and Schr÷ter, 1937|
|Tunisia||Present||Native||Wangerin and Schr÷ter, 1937|
|Canada||Present||Present based on regional distribution.|
|-Alberta||Present||Introduced||Mal et al., 1992|
|-British Columbia||Present||Introduced||Mal et al., 1992|
|-Manitoba||Present||Introduced||1896||Stuckey, 1980; Mal et al., 1992|
|-New Brunswick||Present, few occurrences||Introduced||Mal et al., 1992|
|-Newfoundland and Labrador||Present||Introduced||Mal et al., 1992|
|-Northwest Territories||Absent, intercepted only||Introduced||Mal et al., 1992|
|-Nova Scotia||Present, few occurrences||Introduced||1883||Stuckey, 1980; Mal et al., 1992|
|-Nunavut||Present||Introduced||Stuckey, 1980; Mal et al., 1992|
|-Ontario||Widespread||Introduced||1884||Invasive||Stuckey, 1980; Mal et al., 1992; Treberg and Husband, 1999|
|-Prince Edward Island||Present||Introduced||Mal et al., 1992|
|-Quebec||Widespread||Introduced||1884||Invasive||Stuckey, 1980; Mal et al., 1992|
|-Saskatchewan||Present||Introduced||Mal et al., 1992|
|-Yukon Territory||Absent, intercepted only||Introduced||Mal et al., 1992|
|USA||Present||Present based on regional distribution.|
|-California||Present||Introduced||1948||Invasive||Stuckey, 1980; USDA-NRCS, 2007|
|-Colorado||Present||Introduced||1978||Stuckey, 1980; USDA-NRCS, 2002|
|-Connecticut||Present||Introduced||1895||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Idaho||Present||Introduced||1972||Stuckey, 1980; USDA-NRCS, 2002|
|-Illinois||Present||Introduced||1903||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Indiana||Present||Introduced||1914||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Kansas||Present||Introduced||1968||Stuckey, 1980; USDA-NRCS, 2002|
|-Kentucky||Present||Introduced||1896||Stuckey, 1980; USDA-NRCS, 2002|
|-Maryland||Present||Introduced||1910||Stuckey, 1980; USDA-NRCS, 2002|
|-Massachusetts||Present||Introduced||1831||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Michigan||Present||Introduced||1839||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Minnesota||Present||Introduced||1920-1939||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Missouri||Present||Introduced||before 1936||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Nebraska||Present||Introduced||1973||Stuckey, 1980; USDA-NRCS, 2002|
|-New Hampshire||Present||Introduced||1875||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-New Jersey||Present||Introduced||1840-1859||Stuckey, 1980; USDA-NRCS, 2002|
|-New York||Present||Introduced||1920-1939||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-North Carolina||Present||Introduced||1885||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-North Dakota||Present||Introduced||Invasive||USDA-NRCS, 2002|
|-Ohio||Present||Introduced||1902||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Pennsylvania||Present||Introduced||1901||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-Rhode Island||Present||Introduced||1905||Stuckey, 1980; USDA-NRCS, 2002|
|-South Dakota||Present||Introduced||Invasive||USDA-NRCS, 2002|
|-Utah||Present||Introduced||1943||Stuckey, 1980; USDA-NRCS, 2002|
|-Vermont||Present||Introduced||1898||Invasive||Stuckey, 1980; USDA-NRCS, 2002|
|-West Virginia||Present||Introduced||1858||Stuckey, 1980; USDA-NRCS, 2002|
|Argentina||Present||Wangerin and Schr÷ter, 1937; Torres and Puntieri, 2015|
|Albania||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Austria||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Bulgaria||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Croatia||Present||Native||Wangerin and Schr÷ter, 1937|
|Czech Republic||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Denmark||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Faroe Islands||Absent, formerly present||Wangerin and Schr÷ter, 1937|
|Finland||Present||Native||Not invasive||Wangerin and Schr÷ter, 1937|
|France||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Germany||Present||Native||Royal Botanic Garden Edinburgh, 2007; USDA-ARS, 2007|
|Greece||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Hungary||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Iceland||Absent, intercepted only||Native||Wangerin and Schr÷ter, 1937|
|Ireland||Present||Native||Wangerin and Schr÷ter, 1937|
|Italy||Present||Native||Thompson et al., 1987|
|Netherlands||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Norway||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Poland||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Portugal||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Romania||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Russian Federation||Present||Native||Wangerin and Schr÷ter, 1937|
|-Central Russia||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|-Eastern Siberia||Present||Native||USDA-ARS, 2007|
|-Northern Russia||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|-Russian Far East||Present||Native||USDA-ARS, 2007|
|-Southern Russia||Present||Native||USDA-ARS, 2007|
|Slovakia||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Spain||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|-Balearic Islands||Absent, intercepted only||Wangerin and Schr÷ter, 1937|
|Sweden||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Switzerland||Present||Native||Stuckey, 1980; Mal et al., 1992|
|UK||Present||Native||Royal Botanic Garden Edinburgh, 2007|
|Australia||Present||Present based on regional distribution.|
|-New South Wales||Present||Native||Wangerin and Schr÷ter, 1937; Royal Botanic Garden Sydney, 2007|
|-Queensland||Present||Native||Wangerin and Schr÷ter, 1937; Royal Botanic Garden Sydney, 2007|
|-South Australia||Present||Native||Invasive||Royal Botanic Garden Sydney, 2007|
|-Tasmania||Present||Native||Wangerin and Schr÷ter, 1937; Mal et al., 1992; Royal Botanic Garden Sydney, 2007|
|-Victoria||Present||Native||Wangerin and Schr÷ter, 1937; Royal Botanic Garden Sydney, 2007|
|New Zealand||Present||Introduced||Mal et al., 1992|
History of Introduction and SpreadTop of page
The first mention of L. salicaria in North America was in 1814 (Stuckey, 1980) and it was thought to have been introduced either in ship ballast or with sheep wool to the eastern coast around 1800 (Stuckey, 1980; Thompson et al., 1987). L. salicaria spread slowly along rivers, canals and ditches and moved westwards along the newly constructed Erie Canal (Thompson et al., 1987), and the history of further spread and distribution in North America is well documented (e.g. Stuckey, 1980). From 1850 to 1900, L. salicaria was probably re-introduced with successive waves of European immigrants as a medicinal herb (Thompson et al., 1987) but it was not until the 1930s that the first monocultural populations and rapid expansion of this species westward were observed (Stuckey, 1980), some 140 years after first being introduced. In the 1940s, beekeepers and honey producers began to realize the potential of using this species as a bee forage (Pellett, 1977; Hayes, 1979) and there are reports of beekeepers deliberately spreading L. salicaria seeds along streams and rivers in order to increase the density and number of flowering populations (Thompson et al., 1987). By 1985, L. salicaria was recorded in all states of the USA and southern provinces of Canada between 37°N and 50°N (Edwards et al., 1995), with the highest frequency along the St Lawrence River.
Risk of IntroductionTop of page
Original introductions were accidental, with seed as a contaminant of ballast water, wool and/or live sheep, and these could still be pathways for introduction of this invasive plant elsewhere. Also, commercial nurseries sell cultivars of L. salicaria advertized as being sterile, although research has shown that these cultivars are fertile both when crossed with themselves and with wild L. salicaria populations (USDA-NRCS, 2007). L. salicaria can still be bought from numerous suppliers of ornamental plant seed even though it is a noxious weed in many states of North America. At particular risk may be wetlands of temperate areas of South America where it is not yet present, and also in South Africa (Mgidi et al., 2007).
HabitatTop of page
Where native in Europe, L. salicaria has a wide ecological range, but is generally a species of wet sites. It persists in littoral vegetation, fishponds or streams (Hejný, 1960), rock pools (Hæggström and Skytén, 1987), mudflats (Toivonen and Bäck, 1989), fen meadows, swamp basins, woodlands or open woody margins (Wheeler, 1980a). In England, L. salicaria is a frequent species in open carrs (wet shrub communities) with very rich vegetation and fluctuating water levels, moist woody water margins, beneath woods, and gravel with permanent water 10-15 cm below the surface during the summer (Pearsall, 1918). Usually it is described as a component of early successional vegetation on slightly disturbed or open sites with periodical fluctuations in the water level (Hejný, 1960).
As an exotic species in North America L. salicaria occurs in similar habitats, including littoral vegetation of freshwater marshes and stream margins (Thompson et al., 1987), sedge meadows (Larson, 1989) and road sides (Isabelle et al., 1987). However, in contrast to European native habitats, it is also found in wetlands with high water levels (40 cm or more) in North America (Rawinski and Malecki, 1984; Bastlová-Hanzélyová, 2001). In north-eastern and north-central USA and adjacent provinces of Canada, alluvial floodplains are described as the optimal habitat (Thompson et al., 1987).
Habitat ListTop of page
|Freshwater||Present, no further details||Harmful (pest or invasive)|
|Irrigation channels||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Ponds||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Coastal areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Coastal areas||Secondary/tolerated habitat||Natural|
|Cultivated / agricultural land||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Managed forests, plantations and orchards||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Managed grasslands (grazing systems)||Present, no further details||Harmful (pest or invasive)|
|Rail / roadsides||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Natural forests||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Natural grasslands||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Natural grasslands||Secondary/tolerated habitat||Natural|
|Riverbanks||Principal habitat||Harmful (pest or invasive)|
|Wetlands||Principal habitat||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
As an exotic invasive species, L. salicaria is not generally a weed of agricultural land as it prefers moist to wet habitats, but it may occur at disturbed edges of crop fields in the vicinity of wetlands. The establishment of L. salicaria adjacent to stands of wild rice (Zizania aquatica) in northern California and Wisconsin, USA, means that it may be or become a pest of this crop (Thompson et al., 1987).
Biology and EcologyTop of page
Base chromosome number for L. salicaria has been recorded as n=15 (2n=30), n=25 (2n=50) and n=30 (2n=60), with n=29 (2n=58) rarely observed (Graham and Cavalcanti, 2001). The lowest chromosome counts of 2n=30 were found in Asia, Israel (Dulberger, 1968) and Japan. Intermediate ploidy levels (2n=50) were observed in populations found in northern Germany, north-east Poland and Scandinavia (Mal et al., 1992), while the highest counts of 2n=60 were found throughout Europe; the Czech Republic, Denmark, France, The Netherlands, Norway, Poland, Slovakia and Sweden (Mal et al., 1992). Aneuploids have also been recorded as 2n=45 and 2n=59 (Mal et al., 1992). Chromosome counts reported from North America are 2n=50 and 2n=60 in Ontario, and 2n=60 in Quebec (Mal et al., 1992), indicated Europe rather than Asia as the source of North American germplasm.
Physiology and Phenology
Comprehensive research has been undertaken on the ecophysiology of L. salicaria (Shamsi and Whitehead, 1974a, b; Shamsi, 1974; Shamsi, 1976; Shamsi and Whitehead, 1977a, b), involving basic life requirements and the influence of environmental conditions. L. salicaria is very responsive to differences in nutrient supply, by increasing the root:shoot ratio as nutrient supply decreases, at the expense of dry weight of the stem rather than leaves (Shamsi and Whitehead, 1977a). The proportion of leaves remained similar at all nutrient concentrations tested, although with decreasing nutrient concentration the plant dry weight and number of lateral branches decreased progressively together with a reduction of flowering and fruiting (Shamsi and Whitehead, 1977a).
L. salicaria plants grown at 70% full light exhibit increased leaf area but produced less dry mass and fewer lateral branches as compared to plants grown under full light, and flower later and have smaller fruits with fewer seeds though seed weight was constant (Shamsi and Whitehead, 1974b). Distribution of dry weight between roots, stem and leaves was only moderately influenced by light intensity, with roots forming a high proportion relative to stems and their proportion remained the same, whereas the proportion of leaves increased slightly during ontogeny. Variation in day length had a dramatic effect on growth of L. salicaria plants with 13 h day length appearing to be optimal for the elongation of the main stem, lateral branches and overall growth.
No significant effect of water level on growth and biomass production of L. salicaria was reported from either field (Edwards et al., 1995; Edwards, 1996) or greenhouse experiments (Stevens et al., 1997), although decreasing water availability reduced plant height (Edwards et al., 1995; Stevens and Peterson, 1996). Total biomass content is significantly lower in relatively dry treatments and total stem diameter and porosity and root water content were higher in submersed portions of flooded stems, in both the flooded and the intermediate treatments. Increase in stem porosity and diameter was caused by the presence of aerenchyma in flooded plant parts.
Seed germination occurs in late spring and early summer, beginning generally in late June to early July and continues until end of August or beginning of September. Under experimental conditions the plant usually takes about 10 weeks to flower but under natural field conditions flowering may take up to 12 months. Maturation of the main inflorescence axis follows an acropetal sequence, i.e. basal capsules mature first while the distal part of the inflorescence is still flowering and the plant is green and leafy. The maturation of the axillary lateral inflorescences (on the lateral branches) follows a basipetalous (centrifugal) sequence. Aboveground parts of the plant die back in late autumn and new shoots emerge from the overwintering buds at the top of the rootstock. However, there is also evidence that a minority of established plants in North America can remain dormant above ground for a year and then resume growth in the next growing season (Thompson et al., 1987).
L. salicaria reproduces mostly by seed, although vegetative propagation from rooting nodes has also been observed (Thompson et al., 1987). It is a self-incompatible species. Seed production is dependent on the age, size and vigour of the plant and a single stem can generally produce 900-1000 capsules (Shamsi and Whitehead, 1974a; Thompson et al., 1987), with 83-130 seeds per capsule (Mal et al., 1992). Taking into account the number of stems arising from root, Thompson at al. (1987) estimated the average seed production per plant to be in the order of 2,700,000. Seed viability is very high under laboratory conditions, and seed will even germinate after storage for several years (Wangerin and Schröter, 1937). Although there is no information on the longevity and viability of seeds under field conditions, there can be very large numbers in the seed bank. Welling and Becker (1990) studied seed bank dynamics in North American wetlands and found the mean density of seeds to be 410,000 per m² in the top 5 cm of wetland soil with 37% of these found below a depth of 2 cm.
Optimum temperature for germination is 15-20°C with no germination occurring below 14°C (Shamsi and Whitehead, 1974a). In darkness, germination starts at 20°C and increases rapidly to a maximum at 30°C. Due to these relatively high temperature requirements, L. salicaria seeds can only germinate in late spring or summer in temperate regions. Sand and clay media reduced and delayed germination by 5 and 10 days, respectively, compared to germination on filter paper. L. salicaria can germinate successfully from pH 4 (Shamsi and Whitehead, 1974a) to pH 9.1 (Thompson et al., 1987). Day length (9-16 h light) and different levels of nutrition have no significant effect on the rate or final germination.
L. salicaria is a typical helophyte usually occurring in wet, marshy places, stream banks and ditches at altitudes below 600 m and in low-lying coastal areas (Mal et al., 1992). Temperature is probably the limiting factor to growth and distribution in northern parts of North America (Shamsi, 1974; Thompson et al., 1987). For germination, disturbed sites or open, moist substrates such as water or water edges are necessary and once established, populations may persist for long periods under different conditions at a particular site. It grows better in habitats covered by water temporarily in the spring and which are moist but not covered by water during its active growing period. Optimum substrates for the growth of L. salicaria are moist soils of neutral to slightly acid pH (Shamsi and Whitehead, 1977b). Thompson et al. (1987) found plants growing in a wide range of soil textures and types in North America, from rock crevasses to gravel, sand, clay, organic soils and even crushed-rock ballast on a railroad bridge, suggesting that moisture is the most important factor for growth and reproduction. In the field, L. salicaria can survive in 50% of full sun, but declines in vigour and fails to reproduce at lower light levels (Thompson et al., 1987).
Wheeler (1980a) listed many species in rich-fen vegetation, usually sedge and fen meadow plant communities, where L. salicaria occurs, in association with Caricion davallianae, Junco-Molinion spp., Magnocaricion spp., Phragmition communis and Phragmition spp. In carrs (wet shrub communities), it is found with Alnion glutinosae and Salicion cinereae (mire forests) on nutrient-rich substrates in England and Wales. In the Czech Republic, L. salicaria is a principal species of the Magnocaricion alliance, in association with Caricetum ripario-acutiformis (Hejný, 1960; Dubyna et al., 1993) and other plant species such as Glyceria fluitans, Lysimachia vulgaris, Oenanthe aquatica or Sium latifolium. L. salicaria is facultatively mycorrhizal (Stevens and Peterson, 1996). Although the young foliage of L. salicaria is palatable to grazing animals, both wild and domesticated, the mature plant is much less frequently browsed. Browsing by wildlife may result in a reduction of growth and biomass of L. salicaria (Anderson, 1995), although lower palatability gives it a comparative advantage over more palatable native grasses and sedges in North America and this is thought to be one of the keys reasons for its success as an invasive species of pastures (Thompson et al., 1987).
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Cw - Warm temperate climate with dry winter||Preferred||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
|D - Continental/Microthermal climate||Tolerated||Continental/Microthermal climate (Average temp. of coldest month < 0°C, mean warmest month > 10°C)|
|Df - Continental climate, wet all year||Tolerated||Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)|
|Ds - Continental climate with dry summer||Tolerated||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
|Dw - Continental climate with dry winter||Tolerated||Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean annual temperature (ºC)||5||18|
|Mean maximum temperature of hottest month (ºC)||13||36|
|Mean minimum temperature of coldest month (ºC)||-4||6|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Mean annual rainfall||500||1700||mm; lower/upper limits|
Soil TolerancesTop of page
- seasonally waterlogged
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
Notes on Natural EnemiesTop of page
Batra et al. (1986) identified 120 species of phytophagous insects associated with L. salicaria from surveys in Europe (Italy, Austria, Norway, Sweden and Croatia). This list includes 14 species probably restricted to Lythrum spp. and 64 species of floral visitors associated with L. salicaria. One of the most common of all phytophages was the univoltine weevil Nanophyes marmoratus (Coleoptera: Curculionidae) attacking fruits and destroying up to 69% of the ovules of some plants (Batra et al., 1986). The multivoltine chrysomelids, Pyrrhalta calmariensis [Galerucella calmariensis] and Pyrrhalta pusilla [Galerucella pusilla] (Coleoptera: Chrysomelidae) were patchily abundant in Italy, Austria and Croatia, where dense populations on some plants cause significant (ca. 50%) defoliation. Dasineura salicariae (Diptera: Cecidomyiidae), specific to L. salicaria, is widespread in the cool climates of northern and central Europe, forming galls in apical and axillary meristems which effectively prevent flowering and branching. These galls can reduce foliage production by 75% and reduce the growth of inflorescences and seed production by 80% (Batra et al., 1986). In both Europe and North America the open flowers of L. salicaria are a rich nectar and pollen resource for a wide variety of beneficial insects including pollinating bees, adult parasitic wasps and syrphid flies, as well as for the adults of many phytophagous and saprophagous insects.
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
Long distance dispersal is largely by means of floating seeds (Thompson et al., 1987). Seeds are also light enough to be dispersed by strong wind, but the role of this kind of dispersal seems to be limited and restricted to short distances only, up to 10 m from the parent plant (Thompson et al., 1987).
Vector Transmission (Biotic)
The seeds are likely to be dispersed in mud adhering to aquatic wildlife or via consumption by waterfowl, or attached to livestock, all-terrain vehicle tyres and human footwear, although there is no direct evidence to support any of these potential pathways (Thompson et al., 1987).
In the early 1800s, L. salicaria was probably repeatedly introduced into North America across the Altlantic with ship ballast and imported raw wool or on live sheep (Stuckey, 1980; Thompson et al., 1987).
Purposeful introduction could have occurred at a very early time and has become an increasing problem in the recent history of spread. L. salicaria was valued as a medicinal herb in northern Europe and seeds were probably brought in by immigrants in the 1800s. L. salicaria seeds or rootstalks may also been brought to North America by horticulturists as an ornamental plant for gardens and cultivated sites (Thompson et al., 1987) and are still widely available today. In both North America and Europe, apiculture journals and suppliers have offered seed for sale and provided advice for the growing of L. salicaria and probably distributed plants in some regions.
Pathway CausesTop of page
|Botanical gardens and zoos||Yes||USDA-NRCS, 2007|
|Flooding and other natural disasters||Yes||Yes||Thompson et al., 1987|
|Forage||In hay as feed||Yes||Thompson et al., 1987|
|Harvesting fur, wool or hair||On imported wall||Yes||Thompson et al., 1987|
|Internet sales||Yes||USDA-NRCS, 2007|
|Live food or feed trade||On live sheep||Yes||Thompson et al., 1987|
|Medicinal use||Immigrants bringing it as a medicinal plant||Yes|
|Nursery trade||Yes||USDA-NRCS, 2007|
|Ornamental purposes||Yes||USDA-NRCS, 2007|
Pathway VectorsTop of page
|Clothing, footwear and possessions||Boots||Yes||Thompson et al., 1987|
|Land vehicles||All kinds of treads||Yes||Thompson et al., 1987|
|Livestock||Stuck on mud to, also, more importantly on wild animals||Yes||Thompson et al., 1987|
|Machinery and equipment||Yes||Thompson et al., 1987|
|Commercial nurseries, botanical gardens||Yes||USDA-NRCS, 2007|
|Plants or parts of plants||Yes||Thompson et al., 1987|
|Ship ballast water and sediment||Yes||Thompson et al., 1987|
|Soil, sand and gravel||Ship ballast; ship transport||Yes||Yes||Thompson et al., 1987|
|Water||Yes||Yes||Thompson et al., 1987|
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Growing medium accompanying plants||roots; seeds|
|Stems (above ground)/Shoots/Trunks/Branches||seeds|
|True seeds (inc. grain)||seeds|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
Impact SummaryTop of page
|Fisheries / aquaculture||Negative|
ImpactTop of page
Where L. salicaria is common, direct economic losses are caused by reduced livestock stocking rates and reduction of water flow in irrigation systems. Livestock forage value was reduced in meadows where L. salicaria had established monospecific stands and the palatability of cut hay containing L. salicaria is reduced. L. salicaria is a threat to wetland pastures that typically occur along floodplains and on the peripheries of glacial marshes in central USA and is threatening the production of wild rice (Zizania aquatica) in such areas (Thompson et al., 1987).
Economic ImpactTop of page
Where L. salicaria is common, direct economic losses are caused by reduced livestock stocking rates and reduction of water flow in irrigation systems. Livestock forage value was reduced in meadows where L. salicaria had established monospecific stands and the palatability of cut hay containing L. salicaria is reduced. L. salicaria is a threat to wetland pastures that typically occur along floodplains and on the peripheries of glacial marshes in central USA and is threatening the production of wild rice (Zizania aquatica) in such areas (Thompson et al., 1987). Also, of course, there are significant negative impacts from control efforts, and positive impacts from trading in L. salicaria as an ornamental. Barbier and Knowler (2006) used a model to compare these opposing values using L. salicaria as an example, and concluded that there was a need for an “introducers’ pay” tax to put limits on the uncontrolled spread of trade in invasive species, and spread of the species themselves.
Environmental ImpactTop of page
Impact on Habitat
The dominance of L. salicaria in wetland vegetation causes significant changes in wetland function by altering the timing of litter input and downstream phosphorus load, resulting in accelerated eutrophication of water bodies (Emery and Perry, 1996), with effects on organic matter distribution and soil nitrogen cycling (Fickbohm and Zhu, 2006).
Negative impact of L. salicaria on diversity of plant communities has not been clearly demonstrated and results of various evaluations depend upon the ecological criteria that are used, and some studies even indicate a positive effect of L. salicaria invasion on plant diversity (e.g. Hagar and Vinebrooke, 2004). L. salicaria may suppress the biomass of many wetland plants when germinated and grown simultaneously under laboratory conditions, but it appears to be negatively affected by competition in the field (Shamsi and Whitehead, 1974a, b 1977; Rawinski and Malecki, 1984; Anderson, 1995). Farnsworth and Ellis (2001) quantified multiple stand characteristics of L. salicaria and associated vegetation and found that species richness and stem density of other species were not significantly correlated with the density or percentage cover of L. salicaria stems. With increasing density and total biomass of L. salicaria, the biomass of other species remained constant, or increased at a slower rate and thus appeared to decrease relative to L. salicaria. Anderson (1995) and Treberg and Husband (1999) found no significant relationships between species richness and percentage cover of L. salicaria although the total biomass of all species was significantly, negatively correlated with total biomass of L. salicaria. Once established, individual L. salicaria plants can live for over 20 years (Thompson et al., 1987; Anderson, 1995) and often produce an increasing number of stems each year which may eventually negatively affect community composition and stability.
L. salicaria is an important species for wildlife, with white-tailed deer, muskats, rabbits and several birds including red-winged blackbirds (Agelaius phoeniceus) all observed feeding on L. salicaria (Rawinski and Malecki, 1984; Anderson, 1995). L. silicaria-dominated wetlands were also found to be inadequate breeding habitats for some species of native birds in North America (Maddox and Wiedenmann, 2006). Also, a recent study attempted to assess the effects of invasion on amphibian populations and although results were not significant, Brown et al. (2006) concluded that threats on amphibian populations and food webs may be underestimated, and warrant further investigation.
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Cirsium vinaceum (Sacramento Mountains thistle)||NatureServe NatureServe; USA ESA listing as threatened species USA ESA listing as threatened species||New Mexico||Competition (unspecified); Ecosystem change / habitat alteration||US Fish and Wildlife Service, 2010|
|Cirsium wrightii (Wright's marsh thistle)||NatureServe NatureServe; USA ESA candidate species USA ESA candidate species||Arizona; New Mexico||Competition (unspecified); Ecosystem change / habitat alteration||US Fish and Wildlife Service, 2015|
|Clemmys muhlenbergii (bog turtle)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as threatened species USA ESA listing as threatened species||Connecticut; Delaware; Maryland; Massachusetts; New Jersey; New York; Pennsylvania||Ecosystem change / habitat alteration||US Fish and Wildlife Service, 2001|
|Howellia aquatilis (water howellia)||NatureServe NatureServe; USA ESA listing as threatened species USA ESA listing as threatened species||California; Idaho; Montana; Oregon; Washington||Competition (unspecified)||US Fish and Wildlife Service, 1994|
|Pedicularis furbishiae (Furbish lousewort)||NatureServe NatureServe; USA ESA listing as endangered species USA ESA listing as endangered species||New Brunswick; Maine||Competition - monopolizing resources||US Fish and Wildlife Service, 2007|
|Solidago houghtonii (Houghton's goldenrod)||NT (IUCN red list: Near threatened) NT (IUCN red list: Near threatened); USA ESA listing as threatened species USA ESA listing as threatened species||Ontario; Michigan||Competition - monopolizing resources; Ecosystem change / habitat alteration||US Fish and Wildlife Service, 2011|
Social ImpactTop of page
Wetlands with tall, dense stands dominated by invading L. salicaria can be impenetrable to boats (Thompson et al., 1987) and would reduce hunting opportunities (Blossey et al., 2002).
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Highly mobile locally
- Long lived
- Fast growing
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Altered trophic level
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Modification of hydrology
- Modification of nutrient regime
- Modification of successional patterns
- Monoculture formation
- Negatively impacts agriculture
- Negatively impacts livelihoods
- Negatively impacts aquaculture/fisheries
- Negatively impacts tourism
- Reduced amenity values
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Transportation disruption
- Competition - monopolizing resources
- Rapid growth
- Highly likely to be transported internationally accidentally
- Highly likely to be transported internationally deliberately
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
UsesTop of page
The profuse and attractive floral displays of L. salicaria make the plant well known to gardeners. Its presence is reported in early American gardens (Thompson et al., 1987) and its inclusion in garden and border planting continues throughout Canada and the USA even today, with various cultivars sold in nurseries as potted plants. In areas where it is widespread, L. salicaria is an important source of bee forage, being very attractive to honey bees, although the exact economic benefits of flower production are not known. L. salicaria is now seldom used as a medicinal plant in Europe, but it was highly recommended in early medicine as an astringent, tonic and a blood clotting agent (Thompson et al., 1987), and still has numerous uses today in many parts of Asia, such as a treatment against diarrhoea, chronic intestinal catarrh, haemorrhoids, eczema, varicose veins and bleeding of the gum sin Turkey (Tunalier et al., 2007).
Uses ListTop of page
Animal feed, fodder, forage
- Invertebrate food
- Landscape improvement
- Botanical garden/zoo
Human food and beverage
- Honey/honey flora
- Source of medicine/pharmaceutical
Similarities to Other Species/ConditionsTop of page
In North America, L. salicaria may sometimes be confused with Desmodium canadense, Epilobium angustifolium, Epilobium ciliatum, Liatris spicata and Verbena hastata. In Europe it may be confused with Epilobium angustifolium, Epilobium ciliatum or Lythrum alatum. However, the combination of habitat, square stem and opposite leaves should distinguish L. salicaria from other species.
Prevention and ControlTop of page
Use of flooding and competition from other plant species has been attempted with very limited success. However, flooding to a depth of up to 50 cm for two years had little effect on the stature and reproductive characteristics of L. salicaria and appeared not be a successful method of control (Malecki and Rawinski, 1985). High water level may additionally present stresses for native plant communities. Also, plant competition was only partly successful and results differed greatly depending on the plant species used. Echinochloa frumentacea (Japanese millet) and Polygonum lapathifolium (nodding smartweed) grew well and out-competed L. salicaria (Rawinski, 1982) although Echinochloa walteri (Walter's millet) and Phalaris arundinacea (reed canarygrass) were unsuccessful (Malecki and Rawinski, 1985; Balogh, 1993). Typha x glauca is another potential species on permanently flooded sites (water level always greater than 40 cm) possibly combined with damage by carp (Rawinski and Malecki, 1984). Growth form, habitat type and phenology of L. salicaria indicate that it will not be susceptible to control with fire (Thompson et al., 1987).
Mechanical control, such as mowing, ploughing or hand-pulling give only limited success (Malecki and Rawinski, 1985). Small populations may be successfully controlled by hand pulling, but this method should be avoided after flowering so as not to scatter seeds and plants should be bagged at the site to avoid fragments being dropped along the exit route. Burning is the preferred method for disposal of cut or pulled plants. The date of cutting has an important role in reducing the number of shoots but does not result in permanent control.
Use of herbicides, mostly spot applications of glyphosate, appears to be the most efficient means of control of L. salicaria (Malecki and Rawinski, 1985; Balogh, 1993; Welling and Becker, 1993), although glyphosate and triclopyr amine were both used in Manitoba with success (Henne et al., 2005), and these and several other chemicals were tested alone and in mixtures with success, including triclopyr, 2,4-D dimethylamine and imazapyr (Knezevic et al., 2004). Using glyphosate alone, the timing of applications is important, with late flowering application (13 July) being the most effective with nearly 100% of shoot reduction, as compared to application during the vegetative or early flowering (13 June) stage (Malecki and Rawinski, 1985). Studies on the seed bank dynamics of L. salicaria have shown that for its effective control, a control programme has to operate for a number of years. Single treatments had only a temporary effect due to resprouting from the roots and new plants becoming recruited from the seed bank (Welling and Becker, 1990). The need for repeated chemical treatments over several years can lead to environmental chemical contamination and this type of control has risks associated with negative impacts on native and often threatened flora.
Since the 1990s, great attention has been paid to the biological control of L. salicaria in Canada and the USA. In 1992/3, three insects were approved for release as L. salicaria control agents after laboratory tests in Europe and North America (Hight et al., 1995), although as many as 59 species of phytophagous insects were collected on L. salicaria plants in the north-eastern USA (Hight, 1990). The released agents were two herbivorous insects, Galerucella calmariensis and Galerucella pusilla (Coleoptera: Chrysomelidae) and a root weevil Hylobius transversovittatus (Coleoptera: Curculionidae) and all three established successfully (Hight et al., 1995; Blossey et al., 2002). Malecki et al. (1993) predicted reduction of L. salicaria abundance to approximately 10% of original levels, however, it is expected that plant refugia will remain at sites with high water levels which prevent the development of the root-mining weevil and limit recruitment of the Galerucella spp, and also that plants growing in the shade will also be less likely to be attacked by these biological control agents. They were released in 1684 different wetlands in the USA invaded by L. salicaria (Blossey et al., 2001). Of these, about 50% are regularly monitored using standardized monitoring protocols to assess the impact of the biocontrol agents on L. salicaria. Released herbivore species were established in over 10 provinces of Canada and 30 states of the USA (Blossey et al., 2001) and at several sites had selectively reduced L. salicaria biomass by 95% (Blossey et al., 2002). However, 10 years after release of the two Galerucella species in the state of New York, USA, Grevstad (2006) found no significant impacts at all on L. salicaria populations. Also, mass emergence of adults of Galerucella spp. was also found to result in localized, short-term attack on native species including Decodon verticillatus, Potentilla anserina and Rosa rugosa at some sites (Blossey et al., 2001).
Henne et al. (2005) found that an integrated vegetation management (IVM) strategy using herbicides and biological control outperformed either technique used in isolation. An integrated approach for effective, long-term management through the integration of physical, cultural, mechanical, biological and chemical control strategies was also recommended by Woo et al. (2002).
ReferencesTop of page
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ContributorsTop of page
22/11/2007 Updated by:
Nick Pasiecznik, Consultant, France
Distribution MapsTop of page
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