Cirsium arvense is a perennial species offlowering plant in the familyAsteraceae, native throughoutEurope and westernAsia, northern Africa and widelyintroduced elsewhere.[2][3][4][5] The standard English name in its native area iscreeping thistle.[6] It is also commonly known asCanada thistle andfield thistle.[7][8]
A number of other names are used in other areas or have been used in the past, including:Canadian thistle,lettuce from hell thistle,California thistle,[9]corn thistle,cursed thistle,field thistle,green thistle,hard thistle,perennial thistle,prickly thistle,setose thistle,small-flowered thistle,way thistle, andstinger-needles. Canada and Canadian thistle are in wide use in the United States, despite being a misleading designation (it is not of Canadian origin).[10]
Cirsium arvense is aC3 carbon fixation plant.[11] The C3 plants originated duringMesozoic andPaleozoic eras, and tend to thrive in areas where sunlight intensity is moderate, temperatures are moderate, and ground water is plentiful. C3 plants lose 97% of the water taken up through their roots to transpiration.[12]
Given its adaptive nature,Cirsium arvense is one of the worst invasive weeds worldwide. Through comparison of its genetic expressions, the plant evolves differently with respect to where it has established itself. Differences can be seen in their R-protein mediated defenses, sensitivities to abiotic stresses, and developmental timing.[15]
Cirsium arvense is placed in the subtribe Carduinae, tribe Cardueae of the family Asteraceae. Unlike other species in the same genus, it isdioecious, although male plants sometimes produce bisexual flowers.[16] It also differs from other native North American species in having large roots and multiple small flower heads on a branched stem.[17] Cirsium arvense grows in diverse habitats (ranging from moist places to grasslands, mountain slopes, flooded lands, disturbed sites, etc.) at 100–4,300 m. Its native range is Temperate Eurasia, Northwest Africa. It has been introduced into North America, South America, Africa, Europe, Asia, Australia, and other regions.[18]
Its underground structure consists of four types, 1) long, thick, horizontal roots, 2) long, thick, vertical roots, 3) short, fine shoots, and 4) vertical, underground stems.[19] Though asserted in some literature, creeping thistle does not form rhizomes.[20] Root buds formadventitiously on the thickened roots of creeping thistle, and give rise to new shoots. Shoots can also arise from the lateral buds on the underground portion of regular shoots, particularly if the shoots are cut off through mowing or when stem segments are buried.[20]
Stems are 30–150 cm, slender green, and freely branched,[20] smooth andglabrous (having notrichomes orglaucousness), mostly without spiny wings. Leaves arealternate on the stem with their base sessile and clasping or shortlydecurrent. Theleaves are very spiny, lobed, and up to 15–20 cm long and 2–3 cm broad (smaller on the upper part of the flower stem).
Every plant species has a unique floral fragrance.[21] The fragrance thatC. arvense emits attracts both pollinators and florivores containing compounds that attract each respectively. Honeybees are shown to have the highest visitation rate, followed by other bee species in the generaHalictus andLasioglossum. Hover flies are also commonly seen pollinating the flower heads of this plant.[22] Florivores such as beetles and grasshoppers are commonly seen as well. The compounds found in the fragrance may not be in the highest abundance but they are highly attractive. P-anisaldehyde is found in less than 1%, yet it attracts pollinators such as honey bees.[23] This is thought to be the result of additive and synergistic effects from the blend increasing the attraction to the plant. After pollination, it can be seen that fragrance emission decreases inC.arvense. This is regulated through a regulatory feedback mechanism depending on the pollination status of the plant. This mechanism has only been observed in pistillate plants for dioeciousC. arvense. Fragrance emission increases with age.[24]
The fragrance contains several compounds that attract diverse insects. Looking at certain butterflies species, it can be seen that the fragrance blend is highly attractive to them, being sensitive to their antennae. High antennal response are seen in consequence to the phenylacetaldehyde as well as the terpenes (oxoisophoroneoxide, oxoisophorone, and dihydrooxoisophorone) found in the blend. This was seen in both natural plants emitting the fragrance and emitting the scent synthetically.[25] It is believed that general arousal can be stimulated through exposure of a single compound, whereas the accumulated exposure of all the compounds influence the foraging behaviour of the butterflies.[21]
Theinflorescence compound cyme is 10–22 mm (0.39–0.87 in) in diameter, pink-purple, with all the florets of similar form (no division into disc and ray florets). The flowers are usuallydioecious, but not invariably so, with some plants bearing hermaphrodite flowers.[20] Theseeds are 4–5 mm long, with a featherypappus which assists in wind dispersal.[26][27][28] One to 5 flower heads occur per branch, with plants in very favourable conditions producing up to 100 heads per shoot.[13] Each head contains an average of 100 florets. Average seed production per plant has been estimated at 1530. More seeds are produced when male and female plants are closer together, as flowers are primarily insect-pollinated.[13] The plant can bloom from seed in a year then subsequently the seeds produced can emerge in the following year.[29]
Variation in leaf characters (texture, vestiture, segmentation, spininess) is the basis for determining creeping thistle varieties.[13] According to Flora of Northwest Europe[26] the twovarieties are:
Cirsium arvense var.arvense. Most of Europe. Leaves hairless or thinly hairy beneath.
Cirsium arvense var.integrifolium(Wimm. & Grab). Leaves all entire or the upper leaves entire and the lower stem leaves shallowly and regularlypinnatifid or undulating.
Cirsium arvense var.arvense. Leaves shallowly to deeplypinnatifid, often asymmetrical.
Cirsium arvense var.horridum (Wimm. & Grab). Leaves thick, subcoriaceous, surface wavy, marginal spines long and stout.
The flowers are visited by a wide variety of insects such as bees, moths, wasps and beetles[35] (the generalisedpollination syndrome).[36]The plant is beneficial for pollinators that rely on nectar. It also was a top producer of nectar sugar in a 2016 study in Britain, with a second-place ranking due to a production per floral unit of (2609±239 μg).[37][non-primary source needed]
The species is widely considered aweed even where it is native, for example being designated an "injurious weed" in the United Kingdom under theWeeds Act 1959.[38] It is also a seriousinvasive species in many additional regions where it has been introduced, usually accidentally as a contaminant incereal crop seeds. It is cited as anoxious weed in several countries; for exampleAustralia,Brazil,Canada,Ireland,New Zealand, and theUnited States. Many countries regulate this plant, or its parts (i.e., seed) as a contaminant of other imported products such as grains for consumption or seeds for propagation. In Canada,C. arvense is classified as a primary noxious weed seed in the Weed Seeds Order 2005 which applies to Canada's Seeds Regulations.[39]
A study conducted has shown that with future global atmospheric carbon levels,C. arvense have a risk of increased growth which could expand its range and outcompete native species.[40]
Control methods include cutting at flower stem extension before the flower buds open to prevent seed spread. Repeated cutting at the same growth stage over several years may "wear down" the plant.
Growing forages such as alfalfa can help control the species as a weed by frequently cutting the alfalfa to add nutrients to the soil, the weeds also get cut, and have a harder time re-establishing themselves, which reduces the shoot density.[41]
Orellia ruficauda feeds on Canada thistle and has been reported to be the most effective biological control agent for that plant.[42] Its larvae parasitize the seed heads, feeding solely upon fertile seed heads.[43]
The weevilLarinus planus also feeds on the thistle and has been used as a control agent in Canada.[44] One larva of the species can consume up to 95% of seeds in a particular flower bud.[45] However, use of this weevil has had a damaging effect on other thistle species as well, include some that are threatened.[46] It may therefore not be a desirable control agent. It is unclear if the government continues to use this weevil to control Canada thistles or not.
The rust speciesPuccinia obtegens has shown some promise for controlling Canada thistle, but it must be used in conjunction with other control measures to be effective.[47] AlsoPuccinia punctiformis is used in North America and New Zealand in biological control.[48] In 2013, in four countries in three continents, epidemics of systemic disease caused by this rust fungus could be routinely and easily established.[49] The procedure for establishing this control agent involves three simple steps and is a long-term sustainable control solution that is free and does not involve herbicides. Plants systemically diseased with the rust gradually but surely die. Reductions in thistle density were estimated, in 10 sites in the U.S., Greece, and Russia, to average 43%, 64%, and 81% by 18, 30, and 42 months, respectively, after a single application of spores of the fungus.[50]
Applying herbicide: Herbicides dominated by phenoxy compounds (especiallyMCPA) caused drastic declines in thistle infestation in Sweden in the 1950s.[11] MCPA andclopyralid are approved in some regions. Glyphosate is a non-selective herbicide that can be used when the plant has grown a few inches tall, where the herbicide can be absorbed by the leaf surfaces.[29]
Crop tolerance and weed control ratings were conducted in the spring of 2012, and the Prepass herbicide by DOW AgroSciences was found to be most effective at controlling the species as a weed problem in alfalfa fields.[51]
Like otherCirsium species, the roots are edible, though rarely used, not in the least because of their propensity to induceflatulence in some people. Thetaproot is considered the most nutritious part.[citation needed] The leaves are also edible, though the spines make their preparation for food too tedious to be worthwhile. The stalks, however, are also edible and more easily despined.[52]Bruichladdich distillery onIsle of Islay lists creeping thistle as one of the 22 botanical forages used in their gin, The Botanist.[53]
The feathery pappus is also used by the Cherokee to fletch blowgun darts.[54]
^Lloyd, D. G.; Myall, A. J. (1976). "Sexual Dimorphism in Cirsium arvense (L.) Scop".Annals of Botany.40:115–123.doi:10.1093/oxfordjournals.aob.a085102.
^Blamey, M. & Grey-Wilson, C. (1989).Flora of Britain and Northern Europe.ISBN0-340-40170-2
^Kay, Q. O. N. (1985). Hermaphrodites and subhermaphrodites in a reputedly dioecious plant,Cirsium arvense (L.) Scop.New Phytol. 100: 457-472. Availableonline (pdf file).
^Ziska, L. H. (2003-01-02). "Evaluation of the growth response of six invasive species to past, present and future atmospheric carbon dioxide".Journal of Experimental Botany.54 (381):395–404.doi:10.1093/jxb/erg027.ISSN0022-0957.PMID12493868.
^"Forages in Rotation"(PDF). Saskatchewan Soil Conservation Association. 2016. Archived fromthe original(PDF) on 2016-12-02. Retrieved2016-12-01.
^"Larinus planus".Ministry of Forests, Lands, and Natural Resource Operations. Province of British Columbia, Ministry of Forests. 17 May 2007. Archived fromthe original on 30 January 2019. Retrieved30 January 2019.
^R. C. French, A. R. Lightfield:Induction of Systemic Aecial Infection in Canada Thistle (Cirsium arvense) by Teliospores of Puccinia punctiformis. In:Phytopathology. Band 80, Nr. 8, 1990, S. 872–877,DOI:10.1094/Phyto-80-872
^Berner, D. K., et al. (2013) Successful establishment of epiphytotics of Puccinia punctiformis for biological control of Cirsium arvense. Biological Control 67:350-360.
^Berner, D. K., et al. (2015) Asymptomatic systemic disease of Canada thistle (Cirsium arvense) caused by Puccinia punctiformis and changes in shoot density following inoculation. Biological Control 86:28-35.
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