Marsh plume thistle, European marsh thistle, European swamp thistle, Eurasian marsh thistle, cirse ou chardon des marais, Carduus palustris Linnaeus, Cnicus palustris (L.) Willd.

Preferred conditions for C. palustre germination are a period of moist cold (i.e. cold stratification), followed by full sunlight and warm temperatures (optimal temperature ≥  12°C (54°F)) (Gucker 2009). Germination may occur from April to November, but emergence is most common in late spring and fall. Vegetative cover, shading, and inadequate water conditions may inhibit germination (Fraser 2000).

There are discrepancies in current literature about seed bank longevity (Gucker 2009). In a series of experiments, Pons (1984) determined that high temperatures and reduced access to light induced dormancy in seeds. Pons (1984) also concluded that light is the principle stimulus for germination.

Cirsium palustre prefers moist, acidic soils and is found along roadsides and in wide variety of wetlands, wet forests and forest edges, marshes, and fields. In Michigan, it also colonizes cedar swamps, which are exposed by frequent breaks in cover (Voss 1996).

Populations appear to vary in size and density. Vegetative rosettes often outnumber flowering plants and can densely carpet some areas (Fraser 2000). In Europe, C. palustre behaves as an early successional species, and populations are described as short-lived—declining as rosettes begin to be shaded out by other herbaceous and woody plants (Fraser 2000). Such successional dynamics do not appear to be consistent in invasive populations, where shade does not always limit individual growth and population size (Nordin 2002).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Cirsium palustre has a moderate environmental impact in the Great Lakes.

Realized:
Realized impacts on native species and habitats following establishment have yet to be comprehensively documented or investigated (NatureServe 2010). However, concern exists over the rapidly expanding range of C. palustre in the Great Lakes region (e.g., its southward movement in Michigan; Voss 1996). Cirsium palustre can spread aggressively, resulting in reduced biodiversity and compromised ecological integrity, especially in the wetland ecosystems of Great Lakes islands (Cuthbert et al. 2007, USDA Forest Service 2005b). Its migration is vigorous along roadsides, where it appears to be facilitated by human transportation, including, where applicable, the logging industry (Reznicek et al. 2011).

Potential:
This plant is capable of spreading into open, undisturbed wetlands and forming clumps or impenetrable stands of flowering stalks or carpets of rosettes, potentially displacing native vegetation, altering community structure, and threatening natural diversity (Fraser 2000). Marsh thistle is able to produce 2,000 viable seeds per plants; therefore, only a few plants are needed to have a drastic impact on the seed bank of an area (Fraser 2000, Sheehan 2007). Cirsium palustre poses a threat to C. pitcheri (Torr. ex Eaton) Torr. & A. Gray, which is native to the Great Lakes region and is classified as threatened by the U.S. federal government and the province of Ontario (COSSARO 2011, USDA NRCS 2012a). Native swamp thistle, C. muticum, may also be at risk for adverse competitive effects (GLIFWC 2006). There is some evidence that C. palustre may be allelopathic, although this possibility has not been thoroughly investigated (Ballegaard and Warncke 1985).

In Europe, Cirsium arvense (a native to the Great Lakes) invades native populations of C. palustre and hybridization between the two species has occurred. Such hybridization is possible in North America where these species grow in close proximity, but none has been reported in the Great Lakes (Gucker 2009). Marsh thistle is managed as a high priority species in the Chequamegon Nicolet National Forest (WI), where it is considered a threat to some high quality native areas, but it is not a major concern in all areas (USDA Forest Service 2005a). In British Colombia, C. palustre has been blamed for the degradation of sedge (Carex spp.) meadows (Sheehan 2007). This species could pose a threat to native sedge communities–especially to rare, threatened, or endangered species (USDA NRCS 2012b).

There is little or no evidence to support that Cirsium palustre has significant socio-economic impacts in the Great Lakes.

Potential:
Although it is reportedly not a threat to cultivated agricultural areas, C. palustre may reduce forage quality in damp pastures following establishment. It could form dense clumps in logged cut blocks, competing for moisture and nutrients with tree seedlings planted for reforestation. Tall stems can lead to snow press, permanently damaging tree seedlings (OLA and MAFF 2002).

There is little or no evidence to support that Cirsium palustre has significant beneficial effects in the Great Lakes.

Potential:
Polyphenolic compounds extracted from Cirsium palustre exhibit anti-microbial properties (Nazaruk et al. 2008).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
While there are no specific biocontrol agents for C. palustre (GLIFWC 2006), herbivory by a variety of species may be beneficial but requires additional research.

Promising biocontrol candidates include a European seedhead fly, Terellia ruficauda (Fraser 2000, OLA and MAFF 2002); the seed-eating weevil, Rhinocyllus conicus, currently undergoing experimental trial in the Robson Valley Forest District, British Columbia (OLA and MAFF 2002, USDA Forest Service 2005); and the glassy cutworm, Apamea devastator (native in New York and Ohio; Volger and Stressler 2011). The latter is an indiscriminate herbivore known to feed on C. palustre and may help control marsh thistle; however, this moth feeds on a broad spectrum of additional plants.

Larvae of the artichoke plume moth (Platyptilia carduidactyla) also feed on marsh thistle, but as its common name suggests, this species is considered a pest to artichokes. Furthermore, the moth’s native range is south of the Great Lakes (Winston et al. 2008). Occasionally Cheilosia corydon, a fly native to Italy, feeds on marsh thistle (Winston et al. 2008). This fly was released in Oregon in 1991 to control several invasive thistle populations. However, since its release, C. corydon populations have attacked native and exotic thistles indiscriminately (ODA, Plant Division 2011). Additional insects that feed on and/or use C. palustre for part of their life cycle are listed on the websites of J. Lindsey (http://www.commanster.eu/commanster/Plants/Flowers/SpFlowers/Cirsium.palustre.html) and the Encyclopedia of Life (http://eol.org/data_objects/8731293).

Goats are attracted to the flowering stage of many thistles, including C. palustre. Only about 0.5% of thistle seeds that pass through their digestive systems remain viable, making it unlikely that they would aid in the spread of this species. Effective grazing could reduce marsh thistle populations, although it is unclear whether grazing would ultimately control C. palustre via the trampling of rosettes or facilitate its spread through the creation of safe sites for germination (Fraser 2000). Reseeding of native vegetation may enhance the success of prior control efforts. Moreover, goats do not select for marsh thistle and may also eat native thistles in intermingled communities (Popay and Field 1996).

Van Leeuwen found that a combination of European grazers (rabbits, the hoverfly Cheilosia grossa, and Epiblema scutula) resulted in an approximately 30% reduction in flower heads on Cirsium palustre. Furthermore, plants that had suffered predation had a reduced stem height, resulting in a reduced seed dispersal distance of surviving achenes (van Leeuwen 1983). Additional research is needed to determine if native species of rabbits and insects could have similar results on controlling C. palustre in the Great Lakes.

Physical
All physical control efforts need to be carefully executed and monitored for several years before reducing C. palustre infestations (GLIFWC 2006, Sheehan 2007).

Where infestations are small, hand pulling may be effective. In Chequamegon-Nicolet National Forest (CNNF), Wisconsin, individual plants were mechanically controlled by cutting the root just below the surface with a spade (GLIFWC 2006, USDA Forest Service 2005a). This method is most effective if completed before flowering so that all plant material can be left on site to decompose (Invasive Plant Council of British Columbia 2008). If this method is implemented while flowers and seeds are present, flower heads must be bagged and removed from site; the remaining plant material can be left on site (Invasive Plant Council of British Columbia 2008).

Mowing before plants flower may reduce the release of seeds (OLA and MAFF 2002); however, there is a risk of regrowth with extra flower heads, and extensive mowing of rosettes could promote growth of this early successional species once mowing ceases (Fraser 2000, Nordin 2002). Repeated close mowing can reduce a C. palustre infestation in three to four years (Gumbart 2012.). Mowing a minimum of three times per growing season can be enough to weaken the following year’s population (Boos et al. 2010). However, in a study by Falinska (1999), the density of C. palustre seeds in the soil decreased dramatically as time since last mowing increased, indicating that frequent mowing may actually increase the density of marsh thistle in the seedbank.

Little is known about marsh thistle response to fire as a control strategy (Gucker 2009).

Chemical
Foliar spray with clopyralid or metsulfuron-methyl is the preferred chemical treatment for C. palustre in CNNF, Wisconsin (USDA Forest Service 2005). However, glyphosate must be used in areas that are wet or near open water (USDA Forest Service 2005). Either of these two treatments are most effective if applied in the spring when plants are 6 to 10 inches tall and still in the budding stage or applied directly to the flower heads in the fall (Boos et al. 2010, USDA Forest Service 2005b). To minimize damaging other non-target species when using glyphosate, stems should be cut close to the ground and a small amount sprayed onto the cut area (Sheehan 2007).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.