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TURKEY CREEK CD's NOXIOUS WEED CONTROL PROGRAM FOR PUEBLO COUNTY PAGE 7 OF 10 <br /> heads can still develop viable seeds. The remaining plant should be cut off below the soil <br /> surface to keep it from blooming again. <br /> • Mowing can inhibit flowering. These plants can form flowers at a shorter height after <br /> mowing, so timing is important. Mowing best done once or twice in the early summer <br /> (June)as the plants bolt but just before flowering. <br /> ❖ Herbicide applications to control musk thistle are best done twice per year: once in the spring <br /> before plants have bolted and again in the fall as the plants prepare for winter dormancy. <br /> Herbicide applications will be most effective during these plants'rosette stage.You will be <br /> wasting your time and your money if you spray plants that have already bolted. Plants that have <br /> bolted are not very susceptible to herbicides. Also,if the plant is in bloom when it is sprayed, <br /> the seeds can still mature and disperse. The best times to spray are in early spring(late March <br /> through May) or late fall before the first killing frost(late September or early October). This <br /> will kill the rosettes either as they are newly emerging or going dormant for winter. Remember: <br /> only spray rosettes that have not bolted. An appropriate surfactant mixed with the herbicide <br /> (refer to the label)will aid with the absorption of the herbicide into the plant and you will <br /> achieve better control results. <br /> Canada Thistle(Cirsium arvense) <br /> Canada thistle is a perennial plant with a creeping root system. These plants are long-lived and will <br /> grow and spread year after year. On average, a mature female plant will produce 1,500 seeds per <br /> season with seed viability at approximately 3 years. Canada thistle spreads mainly through its <br /> extensive creeping root system and will form dense colonies. New shoots will emerge from any root <br /> fragmentation. While it is important to stop seed formation, with this plant,it is most important to <br /> stop its vegetative spread. <br /> ❖ Canada thistle is not well controlled by mechanical methods. Do not dig or hand-pull. These <br /> techniques will actually increase your infestation density. Canada thistle will form new sprouts <br /> at each point where its root system is broken. <br /> • Mowing can stress the plants and inhibit flowering. Intensive mowing works best to stress <br /> the plant. Mowing is best done on a monthly basis from early summer to late summer <br /> (June-August). Once the plants have reached 12 inches in height,.commence mowing. Mow <br /> the plants down to 2 to 4 inches in height. <br /> • If the plants have bloomed, flower/seed heads can be removed with clippers. Be sure to bag <br /> and properly dispose of the flower heads because cut-off flower heads can still develop <br /> viable seeds. <br /> ❖ Canada thistle control is increased with cultural methods. Revegetation is very important in <br /> Canada thistle control as the desirable plants will provide competition. <br /> ❖ Canada thistle is best controlled with herbicides and herbicide applications are best done twice <br /> per year. For Canada thistle control,spraying is most effective if done in the fall(September to <br /> early October)before the first killing frost as the plants prepare for winter dormancy. Spring <br /> spraying should be done around the time when flower buds appear on the plants(June). An <br /> appropriate surfactant mixed with the herbicide(refer to the label)will aid with the absorption <br /> of the herbicide into the plant and you will achieve better control results. <br /> • As this species is often found in wet areas,it may restrict the use of certain herbicides. An <br /> aquatic-safe approved herbicide is a great quality to have in an herbicide when applying <br />