Vegetative reproduction in Canada thistle is aided by a fibrous taproot capable of sending out lateral roots as deep as 3' below ground, and from which shoots sprout up at frequent intervals. Advancing the science of gardening and other stuff since 2009. Purple loosestrife has been established for over 200 years, and is quite beautiful, with medicinal properties. Canada thistle rapidly establishes and spreads quickly, replacing native plants. It’s commonly accepted that the time to stop a weed is when it first appears. Canada thistle can also decrease land values due to the potential cost of control and loss of recreational activity due to its’ spiny characteristics. 4. Thickets of thistle crowd out forage grasses in pastures and rangelands, reducing crop yields and productivity. Canada thistle is a perennial plant with an extensive horizontal and vertical rhizome and root system, which can spread 15′ wide and 6-15′ deep. On what basis should folks like you be more or less cavalier? Powered by. Infestations reduce crop yield through competition for water, nutrients and minerals (Malicki and Berbeciowa 1986) and interfere with harvest (Boldt 1981). Even research can be suspect if, as Jeff points out, the thistle isn’t being compared with other weeds as opposed to pristine growing conditions. Livestock do not eat thistles and will not graze between thistle plants on more desirable forage (Batra 1982).”, Invasive.org (linked from .gov sites): update=copyright.getFullYear(); So here’s Ray: Here is a brief summary of the results of a google search of .edu and .gov or .us sites on the subject of Canada thistle or Cirsium arvense as a noxious weed, examining the “whys” by a mostly volunteer* Master Gardener reliant on published literature by reputable sources and charged with fulfilling the Land Grant University charter to bring science based information to the local level. While Canada thistle is the main problem species in this section, there are several other weeds we aim to eliminate such as bindweed, creeping purslane, and pigweed, which have been treated and will be observed as well. Due to its perennial nature, entire plants must be killed in order to prevent regrowth from rootstock. Prairies, barrens, savannas and glades are susceptible, particularly those sites that have been disturbed and are revertin… ECOLOGICAL THREAT: Natural communities that are threatened by Canada thistle include non-forested plant communities such as prairies, barrens, savannas, glades, sand dunes, fields and meadows that have been impacted by disturbance. Cirsium arvense presents an economic threat to farmers and ranchers. Add livestock and dairy interests, and I think you’re tilting at windmills with your fellows on the committee. There are more, but I stopped on page 3 of the 120 page result of the google .edu search. Rose-purple, lavender, or sometimes white flower heads appear from June through October, generally, and occur in rounded, umbrella-shaped clusters. Not Your Average Thistle The key to Canada thistle's weediness is its root system. Species diversity in an “undisturbed” Colorado grassland was inversely proportional to the relative frequency of Canada thistle (Stachion and Zimdahl 1980). Canada thistle. “Thistles are pioneer species and are most often found in sites where the ground cover has been disturbed by grazing, erosion, traffic, or other means. It is a major concern in the Peace River, Omineca … Canada thistle is an alien exotic species capable of crowding out and replacing native grasses and forbs. Grazing animals will not eat anywhere near where Canada Thistle grows, so if you own horses or cows, a bad infestation of Canada Thistle in your pastures can cause problems. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. In Bulgaria Cirsium arvense is a host for the cucumber mosaic virus (Dikova 1989). Canada Thistle is not from Canada. “By 1795, Vermont enacted noxious weed legislation against Canada thistle and, in the early 1900’s, the currently named Noxious Weed Act gave a person the right to eradicate this species wherever they found it without fear of trespassing. As it establishes itself in an area, Canada thistle crowds out and replaces native plants, changes the structure and species composition of natural plant communities and reduces plant and animal diversity. Can we ignore these lists, based on what you say here? Management of Canada thistle can be achieved through hand-cutting, mowing, controlled burning, and chemical means, depending on the level of infestation and the type of area being managed. From Montana: I have to agree with Jeff’s first comment. One of the reasons it has been so successful all over the world is that it can reproduce from both seeds and roots. 2nd cite Colorado: Generally, infestations start on disturbed ground, including ditch banks, overgrazed pastures, tilled fields or abandoned sites. It was introduced to North America in the 1600s, probably in agricultural seed shipments and is now widespread throughout the United States and Canada. Heavy infestations are also commonly found in overgrazed pastures and ranges and may crowd-out and replace native grasses and forbs, decreasing species diversity in an area. The result is a loss of natural diversity. Canada thistle produces an abundance of bristly-plumed seeds which are easily dispersed by the wind. Books: http://www.sustainablelandscapesandgardens.com The problem is …. The wind-dispersed seeds may remain viable for 20 years or more, allowing it to spread quickly and making it difficult to eradicate.”. It is also commonly known as Canada thistle and field thistle.. In the U.S., it is a host for bean aphid and stalk borer, insects that affect corn and tomatoes (Moore 1975), and for sod-web worm (Crampus sp.) It is variable in appearance and spreads in pastures and grasslands by root fragments. Or you can throw the thistle into a barrel of water, let it rot, then water things with that--this can help spread around the minerals the thistle is pulling up, help it do its job, while also killing the thistle plants. Similar plants: Stems of Canada thistle are not spiny in contrast to bull thistle (Cirsium vulgare) and nodding thistle (Carduus nutans). In natural areas where Canada thistle is interspersed with desirable native plants, targeted application of a systemic herbicide such as glyphosate (e.g., Roundup or Rodeo), which carries plant toxins to the roots, may be effective. (When we first moved here, the place was overrun with thistles. 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. Garlic mustard has been here since colonial times and is on many lists, and makes a fine pesto. CONTROL PRACTICES FOR CANADA THISTLE. It grows in circular . Canada Thistle is also a food source for the engrailed moth. Biennial thistles spread only by seed (achenes) that are produced in great number by all the noxious species, ran… “Canada thistle is declared a “noxious weed” throughout the U.S. and has long been recognized as a major agricultural pest, costing tens of millions of dollars in direct crop losses annually and additional millions costs for control. “THREATS POSED BY THIS SPECIES: Natural areas invaded by Cirsium arvense include prairies and other grasslands in the midwest and Great Plains and riparian areas in the intermountain west. “In the Northeast, several weeds including bull and musk thistle, Canada thistle, purple loosestrife (Lythrum salicaria), mile-a-minute (Polygonum perfoliatum), and garlic mustard (Allaria petifolia) are receiving attention [for biological control efforts – ed.] "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors As an analogy, You can call yourself a race car driver, but that doesn’t make you one, and I wouldn’t believe you are one without some kind of proof — like an article showing how well you’d done in a race last week. Canada thistle reduces forage consumption in pastures and rangeland because cattle typically will not graze near infestations. There’s a good reason Canada thistle has a reputation as a highly invasive, aggressive spreader. Posts: 2. posted 7 years ago. In cropland, Canada thistle causes extensive yield losses through competition for light, nutrients, and moisture. If the political process is not the way that legal definitions are made, what do you propose as an alternative? Cirsium arvense threatens natural communities by directly competing with and displacing native vegetation, decreasing species diversity, and changing the structure and composition of some habitats. “Noxious weeds are found in range and pasture as well as noncrop areas and cropland. Persistence is imperative so the weed is continually stressed, forcing it to exhaust root nutrient stores and eventually die.Canada thistle (Cir… In pastures, Canada thistle reduces productivity by crowding out forage species with spiny leaves that deter cattle from grazing. Biennial thistles, such as musk (Carduus nutans L.), plumeless (Carduus acanthoides L.) and bull thistle [Cirsium vulgare (Savi) Tenore], are not as difficult to control as the perennial thistle species, but spread rapidly and can become severe problems in some areas. 1993). But why is it so tough to get rid of Canada thistle and what is the best way to do so? It produces nitrate, which can be toxic to your horse if ingested in large quantities. Once it’s here efforts to stop them aren’t usually that effective (sometimes biological controls will work). I’ll leave cannabis out the discussion, for obvious reasons, but I don’t think it should be “up to me” to decide these things. Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). So, if you disturb the soil and break the rhizomes into pieces, they simply develop into new plants. All biennial thistles considered noxious are native to Europe or Eurasia, and were introduced into North America as seed contaminants. It grows in circular patches, spreading up to 10-12 feet in one season. It is known to harbor other pest species, e.g., insects, and has long been recognized as an agricultural est. Were I in your position, I’d spend my “Political Capital”, on eliminating all the native, beneficial species on the Minnesota secondary noxious weed list bannable at the county level by petition. Weeds can also diminish the quality and palatability of the forage available for livestock grazing, and certain weed species are potentially poisonous to grazing animals. (* about $6500 of my annual salary and benefits comes from fulfilling Master Gardener responsibilities. This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants. It spreads quickly by rhizome and seed production. Ray Eckhart, Master Gardener and loyal blog reader, wrote a long response to Alan’s request for research for the ongoing debate on Canada thistle started a few weeks ago by Jeff. Thank you, Dave. The aesthetic value of a pasture is also impacted by weeds. “Human: Spiny thickets of Canada thistle can restrict recreational access to infested areas.”, South Dakota: Site Map | Legal | Privacy | In fact, improper cultivation can even worsen Canada thistle problems!”, From Pennsylvania: For extensive infestations in disturbed areas with little desirable vegetation, broad application of this type herbicide may be the most effective method. “Canada thistle threatens productivity in both crop and non-croplands. As it establishes itself in an area, Canada thistle crowds out and replaces native plants, changes the structure and species composition of natural plant communities and reduces plant and animal diversity. It spreads quickly by rhizome and seed production. Hand-cutting of individual plants or mowing of larger infestations should be conducted prior to seed set and must be repeated until the starch reserves in the roots are exhausted. Jimsonweed and poison ivy are native and on many state lists. It stores food energy in its extensive root system both to survive the winter and to fuel the plant's reproductive drive the following season. “In alfalfa stands grown for seed production, Canada thistle can reduce yield by 48 percent. “The state regulations of the Kentucky Seed Law classify certain plants such as Canada thistle, johnsongrass, and quackgrass as noxious weeds and prohibit their presence in commercial seed sold in Kentucky.”, National Park Service: In non-cropland ecosystems, Canada thistle can crowd out and replace native grasses and forbs limiting land’s recreational use. Date of U.S. Introduction: 1600s . Both natural and human caused disturbances can create the opportunity for Canada thistle to become established in natural communities.”, Ohio: Because of its contribution to the persistence of the weed, Canada thistle's extensive root system must be the target of an effective control program. It also increases harvesting problems due to seed and forage contamination. An aggressive, spreading root system. Natural communities that are threatened by Canada thistle include non-forested plant communities such as prairies, barrens, savannas, glades, sand dunes, fields and meadows that have been impacted by disturbance. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Ask yourself what weeds you can target where it will make the most difference. Canada thistle invades natural communities primarily through vegetative expansion, and secondarily through seedling establishment. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors 1. which damages corn (Detmers 1927). Kentucky: Deer tend to avoid it, though. document.write("- " + update); 2nd Cite for Pennsylvania: Symptoms of toxicity can range from weakness to convulsions and should be considered a serious medical condition. This isn’t intended to be a defense of Canadian thistle- only a statement of a desire for a more scientific evaluation. Canada thistle is an herbaceous perennial with erect stems 1½" — 4' tall, prickly leaves and an extensive creeping rootstock. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. Obviously the selection process varies widely from state to state. Wildflowers Of WisconsinWild… It boasts an extensive system of rhizomes (underground stems) that can readily produce new shoots. One reference points out that Canadian thistle is toxic to horses — that’s wrong. How can one differentiate between fact and baseless opinion when no actual research is presented as is the case with the danger stated of thistle to pasture. Canada thistle grows in barrens, glades, meadows, prairies, fields, pastures, and waste places. And although I greatly value your opinion, my skepticism dictates more facts and figures before I’d sign a petition to remove canada thistle from the noxious weed list. Canada thistle (Cirsium arvense) is a perennial that has plagued farmers in America since European settlement, and is a Noxious Weed in Pennsylvania. Canada Thistle Where Did it Come From? It is detrimental to natural areas communities where it occurs, particularly non-forested communities, and it can change the natural structure and species composition where it becomes well established. “Noxious weeds are difficult to control and injurious to public health, the environment, roads, crops, livestock and property. Canada thistle is a native plant to regions of Europe and Asia but is considered noxious everywhere else. Canada thistle is a creeping perennial that reproduces from vegetative buds in its root system and from seed. copyright=new Date(); In my opinion Canadian thistle isn’t where it’s at. Other Montana crops seriously threatened by Canada thistle include peas, corn, beans, alfalfa and sugar beets. Canada thistle, flowers in South Dakota - Photo by Chris Evans; University of Illinois. 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