Canada thistle (Cirsium arvense) is a wide-spread invasive weed found in all parts of Clackamas County.Unlike the many native thistles found in Oregon, Canada thistle can quickly overrun an area and displace native plants, reduce agricultural yield, and create problems for grazing animals when they infest a field or pasture.They also cost a lot of money and time to control. Twenty large national parks across the country report it as a serious invasive plant affecting natural resources. Hadroplontus litura, or the Canada thistle stem weevil, is a biological control agent that attacks Canada thistle by larval feeding within the stem, opening the plant up for secondary damage from other organisms such as opportunistic pathogens. However, bull thistle mostly grows where soil has been disturbed, either along roadsides, or in overgrazed pastures. Foliage Leaves are dark green and lanceolate to oblong-lanceolate. Canada thistle (Cirsium arvense) is a wide-spread invasive weed found in all parts of Clackamas County.Unlike the many native thistles found in Oregon, Canada thistle can quickly overrun an area and displace native plants, reduce agricultural yield, and create problems for grazing animals when they infest a field or pasture.They also cost a lot of money and time to control. EIGHTH EDITION. Stem. Canada Thistle ​ … … WEEDS. Weed Information. Wednesday November 13, 2019, 1:00 - 3:30 pm, lunch at 12:00 pm, Mission Leisure Centre, room #4, Copyright 2020, Fraser Valley Invasive Species Society • All rights reserved Mainly grows disturbed areas and can be found on forests, farmland, riparian, and roadsides. It was likely one of the first weeds introduced by North American settlers in the 1600s as a contaminant in seeds. Compound pink to purple flowers in clusters; smaller than other thistles; flowers June to August. SELECTED. Dormant. Fall treatments are better after a light freeze. This species was introduced to North America from … Growth habit: Deep-rooted and colony-forming perennial. Join us online for our 2020 AGM - November 16th, 2020, 10:30 am - 12:00 pm. Learn more about this species: See Fact Sheet - Alberta Invasive Species Council. For Canada thistle, chemical control is needed due to the large tap root and horizontal roots, and because the plant is a perennial. Canada thistle, page 6, for an example of densely clustered flowers on short stalks and musk thistle, page 7, for an example of solitary flowers on long stalks. Local spread of the plant is usually by the root system and long-distance dispersal by the seed. Report a Sighting. See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands Read, understand and follow all label instructions when using any pesticide. WEEDS. … Updated and Reprinted 2002 Updated and Reprinted 2005. Canada thistle may not be completely eliminated even ater multiple herbicide applications over several years . Invasive Species, 2270 Old Penitentiary Road, Boise, ID, 83712, United States The problem is … INVASIVE PLANTS. Canada thistle can reproduce by seed and has male and female flowers on separate plants. UNL web framework and quality assurance provided by the, Apply to the University of Nebraska–Lincoln, Give to the University of Nebraska–Lincoln, Institute of Agriculture and Natural Resources, Strengthening Nebraska's Agricultural Economy. CANADA THISTLE TANSY RAGWORT. It can invade healthy, undisturbed sites as well, out-competing desirable forbs and grasses in pastures and rangeland, reducing biodiversity and forage production. It grows throughout North America, and is considered an invasive species in pastures and forestland. Scientific name: Cirsium arvense L. This plant is a root-creeping herbaceous perennial that can grow up to 2 m tall. PO Box 16021 Sumas Mountain, Rosetta . Canada thistle, also referred to as Canadian thistle, creeping thistle or field thistle, originated in Europe and was brought over to North America in the 1600s. Canada Thistle. Weed Toolbox. Canada thistle is a rhizomatous, perennial, herbaceous plant. It is believed to have come from the eastern Mediterranean region and was likely one of the first weeds that early settlers imported to North America. State Noxious Weed. CANADA THISTLE TANSY RAGWORT. Download the Invasive Species Council of BC’s Factsheet for Canada Thistle here. The standard English name in its native area is creeping thistle. – Creeping thistle, California thistle See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands 1 … Through comparison of its genetic expressions, the plant evolves differently with respects to where it … Be sure to select a product labeled for the site. Canada thistle is found in any type of habitat but normally establishes quickly in disturbed areas. It … New seedlings may continue to emerge for years in treated areas. Chemical Canada Thistle Control Canada thistle can be killed with weed killers. Stressing the plant to force it to use up its root reserves is a key for successful management. Weed Toolbox. State Noxious Weed. Canada thistle can be an invasive species in some natural communities, including prairie potholes and wet or wet-mesic grasslands in the Great Plains and sedge meadows in the upper Midwest (Nuzzo, 1997). Unlike the many native thistles found in Oregon, Canada thistle can quickly overrun an area and displace native plants, reduce agricultural yield, and create problems for … INVASIVE PLANTS. Canada thistle is found in natural areas such as prairies, savannas, glades and dunes where there has been disturbance. Spring and fall applications may be necessary for effective control. Treatments over several years must take place to effect plant invasions. Germination of seed and emergence of plants from rhizomes generally occur at the same time. Despite its name, Canada thistle is native to Europe, parts of North Africa and Asia, including Afghanistan, Iran, Pakistan and China. he months listed below are an approximate range and will vary from year to year and north to south in the state. Height to 4 ft. Foliage irregularly and sharply lobed; margins with short spines. Areas with high invasions can be reduced to dense monocultures that are difficult to control. Consistent cutting of the plant will reduce plant growth and infestations. It is a ruderal species. It was likely one of the first weeds introduced by North American settlers in the 1600s as a contaminant in seeds. Canada Thistle Cirsium arvense. Other names: Canada Thistle, Canadian thistle, Californian thistle, Creeping thistle, Field thistle, Corn thistle, Perennial thistle, Field thistle. Compound pink to purple flowers in clusters; smaller than other thistles; flowers June to August. The Alaska Division of Agriculture classifies Canada thistle as a Top Priority invasive species for … There’s a good reason Canada thistle has a reputation as a highly invasive, aggressive spreader. Canada thistle is a designated noxious weed under the Nebraska Department of Agriculture’s Noxious Weed Program. Currently several weevils and a gall fly have been released to target Canada thistle. Canada Thistle Jan Feb March April May June July Aug Sept Oct Nov Dec Cirsium arvense 4 1 3 2 Management Techniques 1. This makes sense, because bull thistle has a dense, spike-like taproot that can penetrate even the most compacted soils. Mowing can be done prior to flowering to help reduce seed production and force new growth from the roots. Canada thistly is a common weed in agricultural areas and is known to reduce crop yields and forage plants for grazers. It is a non-native invasive species from Europe, and landowners with Canada thistle on their property are obligated to take measures to control it. Jump to: Resources | Images | Distribution Maps | Sources. Canada thistle is especially a problem in the establishment of conservation sites and natural areas. Flowering occurs late spring into summer in response to 14-hour days and are pink to purple in color. Canada thistle, page 6, for an example of densely clustered flowers on short stalks and musk thistle, page 7, for an example of solitary flowers on long stalks. It often outcompetes other plants for new areas to grow. Updated and Reprinted 2014 #100 - 197 North 2nd Ave., Williams Lake, BC V2G 1Z5. Resources. of British Columbia. Plants generally grow in circular patches that are one clone and sex. Most invasive thistles came from Europe in the 1600s. Re-treatment may be necessary until the seed in the soil and the plant’s root reserves are exhausted. When present in cropland, it can reduce yields. Products containing aminopyralid, clopyralid, chlorsulfuron, dicamba, metsulfuron, picloram (Restricted Use), triclopyr, glyphosate (non-selective) and 2,4-D have been shown to work. Canada thistle is a perennial plant that is invasive on the BC coast. It can invade healthy, undisturbed sites as well, out-competing desirable forbs and grasses in pastures and rangeland, reducing biodiversity and forage production. Report a Sighting. Invasive Plants in Northern Virginia: Canada Thistle Cirsium arvense, (Canada thistle), a native of southeastern Europe and the Mediterranean, was brought to North America in early 1700s, probably as a contaminant of crop seed. Scouting, monitoring and proper identification are key factors for management. These biological control measures will not completely manage / control Canada thistle alone, but are an IMP tool and help suppress growth. Invasive thistles can decrease crop yields and reduce forage. However, historians believe it appeared in the United … Weed Laws Reporting Weed Concerns Lawn Care Tips List of Weeds For More Information Weed Identification. Like most invasive plants, Canada thistle, bull thistle, and European swamp thistle (see below) threaten to replace native plants in high quality natural areas, which in turn reduces critical food resources for birds, butterflies, and other wild creatures. The greatest number of plants from rhizomes usually occur in the spring and then another flush in the fall. Invasive Species, 2270 Old Penitentiary Road, Boise, ID, 83712, United States An herbicide treatment will be necessary with either the biological or mowing management options for effective control. The thistle stem weevil larvae (Ceutorhynchus litura) feeds on young thistle plant stems as they elongate. Canada thistle (note that it's NOT 'Canadian' thistle) is in the family Asteraceae. Our native thistles can be much more refined and are exponentially more valuable to wildlife. Foliage Leaves are dark green and lanceolate to oblong-lanceolate. Several different management options will need to be utilized to manage this weed. The exact means of introduction are largely unknown, but it is speculated that they were brought over in farm seeds. Canada thistle (Cirsium arvense) is extremely difficult to kill. Canada Thistle. Canada Thistle. It is also commonly known as Canada thistle and field thistle. However, all introduced thistles should be considered invasive. Canada thistle is an extremely widespread weed of agricultural and ecological areas in the U.S, occurring throughout the northern states and Southwest but is largely absent in the South from Texas to Georgia. Weed Pictures. Perhaps one of the most noxious weeds in the home garden, Canada thistle (Cirsium arvense) has a reputation for being impossible to get rid of.We won’t lie to you, Canada thistle control is difficult and requires a significant amount of effort to be successful, but the effort you put into controlling Canada thistle will pay off when you have a garden that is free from this annoying weed. Download the Invasive Species Council of BC’s Factsheet for Canada Thistle here. These publications and much more are found at http://extensionpubs.unl.edu/. Canada thistle leaves are lance-shaped with irregular lobes and sharp prickly margins. he most important factor in application timing is plant development stage (see Table 2). Plants form a low-growing rosette in the spring prior to bolting in mid-to-late May. However, September is one of the best times to start your assault. It usually is a problem in disturbed areas and Canada thistle can be an invasive species in some natural communities, including prairie potholes and wet or wet-mesic grasslands in the Great Plains and sedge meadows in the upper Midwest (Nuzzo, 1997). Canada Thistle. Infestations of this weed can occur very rapidly. Canada thistle is found across most of North America. In mid-to-late spring, the buds emerge again as rosettes. Canada thistle is spread by wind, birds, or vegetative root growth. Roots can grow deep into the ground. Because many weed killers are non-selective, they will kill anything they touch, so it is best not to use these on windy days. Canada thistle Cirsium arvense (L.) Scop. So, if you disturb the soil and break the rhizomes into pieces, they simply develop into new plants. Canada thistle (Cirsium arvense) is a wide-spread invasive weed found in all parts of Clackamas County.Unlike the many native thistles found in Oregon, Canada thistle can quickly overrun an area and displace native plants, reduce agricultural yield, and create problems for grazing animals when they infest a field or pasture.They also cost a lot of money and time to control. Canada thistle … Canada thistle can grow up to two metres tall at maturity. Hand pulling may be difficult as taproots are extensive and very deep. Similar plants: Stems of Canada thistle are not spiny in contrast to bull thistle (Cirsium vulgare) and nodding thistle (Carduus nutans). Canada Thistle. There’s a good reason Canada thistle has a reputation as a highly invasive, aggressive spreader. Download the Invasive Species Council of BC’s Factsheet for Canada Thistle. It does best in disturbed areas and overgrazed pasture/range. It is an invasive weed native to Europe and Asia. It grows in circular patches by spreading vegetatively through roots and once established, it spreads quickly replacing native plant. Family: Asteraceae (Sunflower family). Mature. Bloom. Stems do not have conspicuous spines. Canada thistle (Cirsium arvense) AK Natural Heritage Program Invasiveness Ranking: 76. of British Columbia. Diseases and insects that normally would affect them are not present in the state, thus heavy infestations often develop. It usually is a problem in disturbed areas and Website developed by AtefDesign.com. It can also be found in roadsides, pastures, rangeland, cropland and riparian areas. Here is the Canada Thistle, Cirsium arvense, a herbaceous plant that is very thorny and is considered a Noxious Weed. Canada thistle thrives in a wide range of soil types but is not tolerant of waterlogged soil or complete shade. NRCS−Montana−Technical Note−Invasive Species−MT-5 1. Canada thistle invades natural areas such as prairies, savannas, open areas in forests, and dunes if some degree of disturbance already exists. It also invades wet areas with fluctuating water levels such as streambanks, sedge meadows, and wet prairies. Appearance Cirsium arvense, a rhizomatous perennial grows from 1-5 ft. (0.3-1.5 m) tall. Why is it invasive? New plants and roots can form from anywhere along the root system. Plants are either male or female (dioecious) so cross pollination is necessary for seed production. Canada Thistle Cirsium arvense (aka Creeping thistle) Overview: A colony-forming, aggressive perennial, that spreads primarily by its creeping root system. There are numerous chemical treatment options available to manage Canada thistle. They start to flower in late spring (April), then seed. Despite its name, the plant was in-troduced from Europe, and is the only thistle, native or introduced, with separate male & … Canada thistle: USDA PLANTS Symbol: CIAR4 U.S. Nativity: Exotic Habit: Forbs/Herbs Cirsium arvense (L.) Scop. Here is the Canada Thistle, Cirsium arvense, a herbaceous plant that is very thorny and is considered a Noxious Weed. It often outcompetes other plants for … Bull thistle is a biennial thistle native to Europe. Canada thistle is a rhizomatous, perennial, herbaceous plant. Description. Canada thistle Cirsium arvense (L.) Scop. It was likely one of the first weeds introduced by North American settlers in the 1600s as a contaminant in seeds. Check out this video made by the University of Wisconsin to help identify the Canada Thistle. Jump to: Resources | Images | Distribution Maps | Sources. About Canada Thistle Despite its common name, this invasive thistle is not native to Canada, but actually native throughout Europe and Northern Asia. Biology and Identification. The extensive root system allows the plant to survive periods of drought and access water & nutrient reserves far below the roots of na- … Canada Thistle is the only species of today's Weed Control Act that was already regulated in the first Alberta weed regulation in 1907. Outcompetes native vegetation and can establish dense stands. NOXIOUS. Reprinted 1998 Updated and Reprinted 2000.         Canada. First Printing 1996. Resources. You can find very thorough treatment instructions using the Midwest Invasive Plant Network (MIPN) control database (http://mipncontroldatabase.wisc.edu/). About This Subject; View Images Details; View Images; Go To Host Page ; Overview. Thistle plants produces many seed heads on erect branching stems. The current Thistle Law is directed at only three of the five species. Hand-pulling and cultivation are often ineffective control mechanisms because new plants sprout from root pieces that snap off. Beck, K.G., “Canada Thistle”, Colorado State University, Fact Sheet 3.108, Grover, A., et al, “Managing Canada Thistle”, Penn State, Conservation Reserve Enhancement Program (CREP) Technical Assistance Series Fact Sheet 1, Stubbendieck, J., et al, “Weeds of the Great Plains”, Nebraska Department of Agriculture, 2019, Wilson, R., “Noxious Weeds of Nebraska Canada Thistle”, University of Nebraska, EC171, 105 Ag. Roots can spread laterally 12 to 18 feet and be as deep as 6 to 15 feet. Canada thistle (Cirsium arvense) AK Natural Heritage Program Invasiveness Ranking: 76 Identified as a prohibited noxious weed in Alaska (11 AAC 34.020), and in 34 other states. Control of Canada Thistle in CRP and Other Noncrop Acreage • FNR-436-W Herbicides that are efective on Canada thistle will injure or kill most broadleaf plants (including legumes) and … Each thistle plant can produce 1,000 up to 1,500 seeds per shoot. About This Subject; View Images Details; View Images; Go To Host Page ; Overview. The addition of a non-ionic surfactant to the herbicide mix will aid in control. Early Detection and Rapid Response (EDRR) is a concept to identify potentially invasive species prior to or just as the establishment of the invasive is taking place. Though the mechanism for long distance seed dispersal is not known, irrigation water is another reported possible means of transport. Legal status: Canada thistle is considered a noxious weed in 46 states including Indiana. Perennial forage plants and winter annual cereals compete most effectively with Canada thistle. It has purple flowers and spiny, glossy leaves arranged alternately along its stem and many branches. About Canada Thistle Despite its common name, this invasive thistle is not native to Canada, but actually native throughout Europe and Northern Asia. Invasive Plants in Pennsylvania: Canada Thistle (PDF | 576 KB) Pennsylvania Department of Conservation and Natural Resources. Canada thistle is found across most of North America. Weed Laws Reporting Weed Concerns Lawn Care Tips List of Weeds For More Information Weed Identification. The plant was called “Canada” thistle because early New England residents blamed its emergence on French traders from Canada. The Alaska Division of Agriculture classifies Canada thistle as a Top Priority invasive species for … Habitat. It boasts an extensive system of rhizomes (underground stems) that can readily produce new shoots. (March-May) Hand Pull. Prevention is the best and cheapest management option. Leaf. Canada thistle is not palatable to livestock. Roots can grow deep into the ground.         Abbotsford BC, V3G 0C6 Canada thistle is especially a problem in the establishment of conservation sites and natural areas. Canada thistle is an extremely widespread weed of agricultural and ecological areas in the U.S, occurring throughout the northern states and Southwest but is largely absent in the South from Texas to Georgia. They are weak during germination, but after 7 to 8 weeks they are able to regenerate. Canada thistle. Despite its name, this invasive thistle is not from Canada. Many invasive weed species are a problem of natural areas but Canada thistle is a serious problem not only in natural areas but also in agriculture, landscapes, lawns and right of ways. Five invasive thistles identified in Oklahoma are from Europe and Asia and represent four genera. Thistle stem gall fly larvae (Urophora cardui) attack the primary lateral stems. Download the Invasive Species Council of BC’s Factsheet for Canada Thistle here. TUTORIAL ON USING A DICHOTOMOUS KEY Dichotomous keys consist of a series of two mutually exclusive statements, known as couplets. Canada thistle is a non-native perennial forb that reproduces/spreads from seed and rhizomes. This high fecundity allows the Canada thistle to be reintroduced frequently which is a key component for invasives to become established. There are also several pathogens that may help suppress thistle growth, a thistle rust fungus, white mold and a bioherbicide (Pseudomonas syringae). thistle spreads quickly through horizontal roots. Search “thistle” or “invasive”. By the end of the century is was already recognized as a noxious weed in crops, and it is now recognized… It also invades croplands, pastures, lawns, gardens, roadsides, ditches and waste sites. Mowing is effective prior to flowering stages. Common names: creeping thistle, field thistle, perennial thistle; Scientific names: Carduus arvensis; Cirsium incanum; Ecological threat: It invades undisturbed areas such as prairies, savannas, glades, dunes, streambanks, sedge meadows and forest openings. Updated and Reprinted 2014 #100 - 197 North 2nd Ave., Williams Lake, BC V2G 1Z5. Seed can germinate on the soil surface or to a depth of 3 inches in the soil. Updated and Reprinted 2007 Reprinted 2010. a.k.a. But these descriptions should be restricted to the invasive non-native thistles, like bull thistle (Cirsium vulgare) and Canada thistle (Cirsium arvense); they are the bane of agricultural growers and anyone with ecologically sensitive areas to maintain. Once Canada thistle has invaded, it is very important to maintain soil fertility and moisture at optimum levels to favor crop or pasture plant establishment and growth. This high fecundity allows the Canada thistle to be reintroduced frequently which is a key component for invasives to become established. Canada Thistle ( Cirsium arvense ) QUICK IDENTIFICATION. 1 … It is considered a noxious weed under the BC Weed Control Act. Similar plants: Stems of Canada thistle are not spiny in contrast to bull thistle (Cirsium vulgare) and nodding thistle (Carduus nutans). Canada thistle plants are usually 2 to 4 feet tall or taller with alternate dark green leaves and an extensive root system. Seed can remain viable over 20 years. It is a major concern on the coast and is a widespread problem throughout the province. Bull thistle is a biennial thistle native to Europe. Some parts of this site work best with JavaScript enabled. Having well-established perennial grasses and forbs on a maintained pasture or rangeland with proper grazing and rotational grazing techniques can go a long way to prevent its establishment. Where did it come from? Canada Thistle Despite its common name, this invasive thistle is not native to Canada, but actually native throughout Europe and Northern Asia. Identified as a prohibited noxious weed in Alaska (11 AAC 34.020), and in 34 other states. The developing larvae in the stem causes the plant to form a gall on the stem which weakens the plant (Photo 2). Canada thistle leaves are lance-shaped with irregular lobes and sharp prickly margins. Flowering Canada thistle. TUTORIAL ON USING A DICHOTOMOUS KEY Dichotomous keys consist of a series of two mutually exclusive statements, known as couplets. Introduced into the United States around 1750. Invasive Species Program; Species ; Plants; Canada Thistle; Canada Thistle. EIGHTH EDITION. It has now become an invasive species, with its aggressive growing and ability to spread at a rapid rate. Due to its perennial nature, entire plants must be killed in order to prevent re-growth from rootstock. Cirsium arvense is a perennial species of flowering plant in the family Asteraceae, native throughout Europe and western Asia, northern Africa and widely introduced elsewhere. It has now become an invasive species, with its aggressive growing and ability to spread at a rapid rate. So, if you disturb the soil and break the rhizomes into pieces, they simply develop into new plants. Currently several weevils and a gall fly have been released to target Canada thistle. NOXIOUS. Invasive Species Program; Species ; Plants; Canada Thistle; Canada Thistle. Seed can be spread by wind, water, livestock, wildlife, vehicles, contaminated crops, and humans. In small areas this is your most effective choice. Hadroplontus litura, or the Canada thistle stem weevil, is a biological control agent that attacks Canada thistle by larval feeding within the stem, opening the plant up for secondary damage from other organisms such as opportunistic pathogens. An Integrated Pest Management plan (IPM) can be developed to manage, contain and eradicate the invasive species before it can spread further. Learn more about this species: See Fact Sheet - Alberta Invasive Species Council. Reprinted 1998 Updated and Reprinted 2000. Invasive Plants in Pennsylvania: Canada Thistle (PDF | 576 KB) Pennsylvania Department of Conservation and Natural Resources. The introduced Canada thistle, Matt pointed out, can choke out all sorts of native vegetation as well as native thistles. Tank mixes of several of these compounds may provide better control. Make sure the entire root system is removed and bagged or this will be ineffective. Creeping thistle is a herbaceous perennial plant growing up to 150 cm, forming extensive clonal colonies from thickened roots that send up numerous erect shoots during the growing season. First Printing 1996. Habitat. Canada thistle, also referred to as Canadian thistle, creeping thistle or field thistle, originated in Europe and was brought over to North America in the 1600s. Unlike most of our thistles, he said, Canada thistle is a perennial that forms clonal root networks. Field Guide to. Canada Thistle Cirsium arvense. Each individual plant can produce 1000 to 1500 seeds. Hand-pulling and cultivation are often ineffective control mechanisms because new plants sprout from root pieces that snap off. It grows throughout North America, and is considered an invasive species in pastures and forestland. Canada Thistle is the only species of today's Weed Control Act that was already regulated in the first Alberta weed regulation in 1907. Seeds can disperse through pets, wild animals, clothing, vehicles, and wind. The adults also feed on the plant foliage in the early spring, although their effect on the plant is limited. Twenty large national parks across the country report it as a serious invasive plant affecting natural resources. Height to 4 ft. Foliage irregularly and sharply lobed; margins with short spines. Up its root reserves is a wide-spread invasive weed found in all parts of County! A noxious weed List meaning you must prevent the spread of this plant is usually by the root.. Plant ( Photo 2 ) has purple flowers in clusters ; smaller than other ;. Not present in the first Alberta weed regulation in 1907 are either or... And help suppress growth irregular lobes and sharp prickly margins here is only! 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System of rhizomes ( underground stems ) that can readily produce new shoots California thistle Scientific name: arvense. Perennial that can penetrate even the most compacted soils and ability to spread at a rapid rate invasive weeds.! Feet tall or taller with alternate dark green and lanceolate to oblong-lanceolate this Subject ; View Images Go. Plant ( Photo 2 ) invasives to become established a dense, spike-like taproot that can up... Eradicate it consist of a series of two mutually exclusive statements, as. ; margins with short spines Species Program ; Species ; plants ; Canada thistle and thistle. High fecundity allows the Canada thistle ; Canada thistle is on control noxious weed called! 12 to 18 feet and be as deep as 6 to 15 feet for grazers manage / Canada... Page ; Overview Pennsylvania Department of Conservation sites and natural areas a widespread problem throughout province! The best times to start your assault Table 2 ) plant growth and infestations noxious weed in Alaska 11. However, September is one of the first weeds introduced by North American settlers in the 1600s fall!