The bracts do not have spines on their tips. This species is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Control List meaning that efforts must be made to prevent the spread of seeds or other propagating parts. Mechanical control can be done by repeated hand pulling or using a tool such as shovel. CSU Extension - A division of the Office of Engagement. As mentioned earlier, they thrive in disturbed soils.) When Canada thistle infestations occur in situations where root growth would be restricted, such as habitats with high water tables, begin mowing when it is 12 to 15 inches tall. Physical description Canada thistle is a perennial that spreads by seed and an underground system of vertical and horizontal roots. Canada thistle reduces forage consumption in pastures and rangeland because cattle typically will not graze near infestations. Canada thistle is a creeping perennial that reproduces from vegetative buds in its root system and from seed. Canada thistle, flowers in South Dakota - Photo by Chris Evans; University of Illinois. – Creeping thistle, California thistle Scientific name: Cirsium arvense L. Family: Asteraceae (Sunflower family) Description Origin: Eurasia and North Africa. Canada thistle seedlings develop a perennial habit (the ability to reproduce from their root systems) about seven to eight weeks after germination. Also, these small roots can survive at least 100 days without nutrient replenishment from photosynthesis. Seedlings: Cotyledons are oval to round and pale green in color. Canada thistle (Cirsium arvense) is native to Europe and nothern Africa, and was introduced to North America soon after the arrival of European settlers. Canada thistle emerges from its root system in mid- to late spring (late April through May) and forms rosettes (Figure 2). If pulling plants, leave plants on-site to decompose or follow Minnesota Department of Agriculture guidance for plant disposal. Cultural control. Our physical location is 1311 College Ave, Fort Collins, CO. Having website issues? Canada thistle develops seed sparingly and may produce 1,000 to 1,500 seeds per flowering shoot. However, competition alone seldom is effective against Canada thistle. Canada Thistle is a problem in pastures, roadsides, agricultural fields, landscapes, and yards. Mowing at hay cutting stimulates new Canada thistle shoots to develop from its root system. Biological control insects are not considered a recommended means of control in Minnesota at this time. It is difficult to control because its extensive root system allows it to recover from control attempts. Female flowers have a pleasant vanilla-like aroma. For information on the state’s response, visit the Department of Health website. Canada thistle has small seeds with feathery, white tufts to help with wind dispersal, although research has found that most seeds land near the parent plant. Each small section of root can form a new plant, enabling the plant to spread vegetatively. Canada thistle. *Colorado State University Extension weed science specialist and professor, bioagricultural sciences and pest management. Mowing alone is not effective unless conducted at one-month intervals over several growing seasons. Horizontal roots may extend 15 feet or more and vertical roots may grow 6 to 15 feet deep. Canada thistle develops seed sparingly. Herbicide control of Canada thistle is most effective when you apply the herbicide in spring (April, May or June) or fall (September or October). Sometimes plants are planted purposefully. Leaves are deeply divided and have spines along the edges. Apply 2,4-D, 2 quarts per acre (A), in spring when Canada thistle is 10 to 15 inches tall, in pre-bud to early bud growth stages. Its invasiveness was soon recognized, and in 1795 Vermont lawmakers created the first noxious weed law in the United States in an attempt to stop the spread of Canada thistle. Also, wind may help disperse seed, but most often, the feathery pappus breaks off, leaving the seed attached to the parent plant to be dispersed by other means. Report a Sighting. Despite its name Canada thistle, this plant is not native to North America. Webmaster | field thistle. canada_thistle_cirsium_arvense_flower_072212_AR.jpg. Maintain fertility and, if possible, moisture at optimum levels to favor grass or alfalfa growth. Revised 11/13. A Canada thistle management system can start with crop or grass competition combined with herbicides, with the field rotated to alfalfa when the management plan ends. For prescribed burns, the goal is to favor native grasses over Canada thistle. Colorado State University data also indicates that Banvel/Vanquish/Clarity or Telar are effective when combined with 2,4-D as a split-season application. DNR RESPONSE TO COVID-19: For details on adjustments to DNR services, visit this webpage. Research has shown that biological and chemical controls are compatible for musk thistle. Refer to Table 1 for use rates and application timing and always read the herbicide label before using the product. The plant is dioecious, resulting in colonies of either all male or all female plants. Generally, infestations start on disturbed ground, including ditch banks, overgrazed pastures, tilled fields or abandoned sites. Other Names: chardon des champs, Canadian thistle, Creeping thistle, Field thistle, chardon du Canada Family: Composite or Aster Family ( Compositae ) General Description: Perennial, reproducing by seed and by horizontal roots which produce new shoots, often forming dense patches. Seeds can separate from the white tufts. Description. Canada thistle can reproduce by seed and has male and female flowers on separate plants. CSU research shows that aminocyclopyrachlor (one of the Perspective components) and aminopyralid (Milestone) are absorbed primarily by the root system. Chemical control. Introduced perennial from Eurasia. This species was introduced to North America probably as a contaminant in seed or forage. is a colony-forming perennial. In 2002, the Colorado Department of Agriculture surveyed counties and while incomplete, the results showed more than 100,000 acres infested with Canada thistle (Figure 1). Mowing hay meadows can be an effective tool if combined with herbicide treatments. It will not adequately establish in a well-developed Canada thistle infestation. Plants 2 to 4 feet tall, branched above, with a well-developed, freely branching, fibrous root system. Canada thistle allocates most of its reproductive energy into vegetative propagation. CSU A-Z Search Plants that germinate from seed do so at about the same time as root-derived shoots. Plants are either male or female (dioecious) so cross pollination is necessary for seed production. Caution: Plants have spines along leaves. Take care to remove as much of the root as possible. Re-treat in fall with Banvel/Vanquish/Clarity (2 quarts/A) or Telar (1 ounce/A) to re-growth. Canada thistle is difficult to control and re-treatment for one to three or more years after the initial application is common. Vegetative Characteristics A mature Canada Thistle … 1. Galls that form near the terminal meristems (e.g., where flowers develop) keep the weed from flowering and reduce seed set. Flowers are pink, bristly, 1/2 inch long and wide. Scientific Name: Cirsium arvense (L.) Scop. Miscellaneous: Canada thistle was the first weed declared noxious in the U.S., given this status by Vermont in 1795. Life Cycle: Perennial General Description: A rhizomatous perennial with lobed, spiny leaves and pink flowers. The female lays eggs on the underneath side of Canada thistle leaves in early spring. Combining control methods is the best form of Canada thistle management. Canada thistle grows in a variety of soils and can tolerate up to 2 percent salt content. Cultivation:The preference is full sun, moist to mesic conditions, and a fertile soil consisting of clay-loam. Additionally, root nutrient stores decrease after mowing because the plant draws on them to develop new shoots. Biological control insects for Canada thistle are commercially available, but Canada thistle control results have been variable and the insects' impacts on native thistles have not been thoroughly tested. Emergence. Disclaimer | Larvae burrow into shoots. A flush can occur anytime during the growing season when soil moisture is adequate. 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