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i <br /> i <br /> Rangeland-Pasture Recommendations <br /> Diffuse knapweed Identification and <br /> Management <br /> Diffuse knapweed (Centaurea diffusa) is a non-native biennial forb that <br /> reproduces solely by seed. A biennial is a plant that completes its lifecycle within <br /> two years. During the first year of growth, diffuse knapweed appears as a rosette <br /> in spring or fall. During the second year in mid to late spring- the stem bolts, <br /> flowers, sets seed, and the plant dies. Once the plant dries up, it breaks off at <br /> ground level and becomes a tumbleweed allowing seeds to be dispersed over <br /> long distances. A prolific seed producer, diffuse <br /> knapweed can produce up to 18,000 seeds per plant. <br /> s Therefore, the key to managing this plant is to <br /> prevent seed production. <br /> Diffuse knapweed can grow 1 to 3 feet tall, <br /> and is diffusely branched above ground. This gives <br /> the plant a ball-shaped appearance and tumble- <br /> weed mobility when broken off. Leaves are small, <br /> and are reduced in size near the flowering heads. <br /> Flowers are mostly white, sometimes purple, urn- <br /> shaped, and are located on each branch tip. Bracts <br /> that enclose the flowerheads are divided like teeth <br /> ' of a comb, and are tipped with a definite slender <br /> spine. Upon drying, the bracts become rough, <br /> rendering them injurious to the touch. <br /> NYou can expect to see flowers from July . . <br /> through August. Seed set usually occurs <br /> by mid-August. <br /> iDiffuse knapweed tends to invade <br /> disturbed, overgrazed areas. r„ <br /> It may also be found on rangeland, <br /> roadsides, riparian areas, and trails. It is a <br /> tough competitor on dry sites and rapidly <br /> invades and dominates disturbed areas. <br /> Once established, diffuse knapweed <br /> outcompetes and reduces the quantity of desirable native species such as <br /> ' perennial grasses. As a result,biodiversity and land values are reduced, and soil <br /> erosion is increased. <br /> On the backside of this sheet are diffuse knapweed management <br /> i recommendations. If you have any questions,please contact the Weld County <br /> Public Works Dept.,Weed Division at(970) 304-6496, ext. 3770. Please visit our <br /> website www.weldweeds.org. <br /> 1 <br /> 1 <br />