Canada thistle has male and female flowers on separate plants (dioecious)and seed production requires the presence of both plants. Canada Thistle. of crop seed, as early as the late eighteenth century (it was declared a noxious weed in Vermont in 1795). Canada Thistle and its Control . Very competitive with field crops and forages. | File photo One of Canada’s nastier pests originally emigrated from Europe and then made its way west. Damage In alfalfa stands grown for seed production, Canada thistle can reduce yield by 48 percent. Horizontal roots may extend 15 feet or more and vertical roots may grow 6 to 15 feet deep. Mowing: Mowing just before flower buds open can stop the development of Canada thistle seeds. Similar plants: Stems of Canada thistle are not spiny in contrast to bull thistle (Cirsium vulgare) and nodding thistle (Carduus nutans). Canada thistle, an invasive species of the United States and Canada, is well known for production of high numbers of seeds, asexual reproduction, and wide environmental tolerance. This is an extremely aggressive plant, which spreads quickly through underground rhizomes, as well as by seed production. It was ranked as “urgent“ for control in a review of exotic plants at Pipestone National Monument, Minnesota (Hiebert and Stubbendieck, 1993). Take a minimum of 20 weed counts across the field. Canada thistle generally spreads from field to field in contaminated crop seed or forage. Canada thistle is a non-native perennial forb that reproduces/spreads from seed and rhizomes. Since this species is dioecious, that is the staminate and pistillage heads are borne on different plants, two individuals are necessary for seed production. Canada thistle also harbors insects and is an alternative host for some diseases. Canada thistle is also prolific in seed production at 700 seeds per stem. Canada thistle rosette form with spiny tips and wavy leaves. An aggressive, spreading root system. Flowering occurs late spring into summer in response to … Canada thistle produces about 700 seeds per plant. Canada thistle is a creeping perennial that can be controlled with fall spraying, in conjunction with other management options in the spring. Cross pollination is necessary for seed production, therefore, both male and female plants must be present at a site for seed production to occur. It is also commonly known as Canada thistle and field thistle.. If a patch of Canada thistle is started from one seed and spreads or its roots are dragged throughout a field, it still represents the offspring from one seed. Wind and moving water can distribute seeds, but seeds often stay within a few meters of the parent plant. In contrast to Pammel, Hayden found that seed production in Canada thistle was quite common in Iowa. Management practices are expensive and can damage Flowers are about ... Another thistle to look out for is Canada thistle. Hayden developed a map of Canada thistle distribution in Iowa in the 1930's, and numerous infestations were reported in every county. In Indiana, Canada thistle normally initiates growth in spring, reaches the flower-bud stage the first week in June, and full flower about the third week of June. Thus the species rapidly spread across Iowa in approximately 30 years. Quick Facts… is a creeping perennial that reproduces from seed and vegetative roots. New Canada thistle shoots developing from buds on roots. Within a Canada thistle population, some seed remains in the flower head or falls at the base of the plant. Canada Thistle: Seed Production, Germinability, and Viability GARY E. LARSON1, TIM A. WITTIG, KENNETH F. HIGGINS, BRENT TURNIPSEED, AND DAWN M. GARDNER Department of Biology and Microbiology (GEL) Canada thistle develops fewer seeds than Musk thistle, with a range of 1,000 to 1,500 seeds per flowing shoot (Beck 2008). 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