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Musk Thistle Identification and Management <br /> plumose bristles that appear barbed un- <br /> der magnification. Musk thistle produces `} o <br /> many flower heads.The tallest shoots ., <br /> flower first;lateral shoots develop in leaf <br /> axils.A robust plant may produce 100 or <br /> more flowering heads. Reproduction is <br /> usually via out-crossing through insect <br /> pollination, but self-pollination also <br /> occurs.Flowers emerge in May through <br /> September.Seeds develop shortly after <br /> flowers emerge. Flower buds can contain <br /> viable seeds from self-pollination.Seeds ,. <br /> can mature on severed bud and flower- <br /> heads.Seeds remain viable in the soil for .' <br /> u to about 14 ears.Seeds can ermi- <br /> ®eru<encaey.oHst�t�unw�ryry P Y germi- <br /> nate and emerge from spring through <br /> M usk thistle Carduus nutans L. is a <br /> fall. <br /> non-native biennial forb that re- <br /> produces solely by seed.During the first <br /> usk thistle habitat is found in a <br /> year of growth,a rosette forms in spring Mvariety of environments extend- <br /> or fall. During the second year in mid to ing from shortgrass prairie to alpine. <br /> late spring,the stem bolts,flowers,sets <br /> seed, and the plant dies. It is strongly associated with heavily <br /> disturbed sites,where over-use occurs w <br /> or where site conditions are poor due <br /> M usk thistle can grow up to 6 feet <br /> to land management practices.This <br /> tall.The leaves have spines,are includes over-grazed areas, large fires, <br /> waxy,and dark green in color with a <br /> prominent light green to white midrib <br /> trails,ditches and roadsides.Infested V1 <br /> 6 Les MehrhuH,olscnverLlfe org <br /> livestock pasturs suffer from significantly � <br /> that can be seen from a distance. Leaves decreased carrying capacity. <br /> are dentately lobed; leaf bases some- i <br /> times extend down below the point of ecause musk thistle reproduces <br /> attachment.The terminal flower heads <br /> are purple, large in size(1.5 to 3 inches solely from seed,the key for suc- ,•_ t/1 <br /> cessful management is to prevent seed (— <br /> in diameter)and bend over as if nod- production.Once flowers emerge and <br /> ding.These flower heads are made up of start to produce seed,effective manage- <br /> only disk flowers.They are surrounded ment options will become limited.Once <br /> by numerous,wide and stout lance- sites are infested, musk thistle can form <br /> shaped, spine-tipped bracts that resem- dense stands. Prevention,adjusting land <br /> ble an open pineapple.The pappus has management practices,a robust inte- <br /> grated treatment plan and <br /> 2015 Quarter Quad Survey restoration are critical to <br /> - - -- - eliminating this species. 1. Leaf with white <br /> Musk Thistle mfsoa�em�Fcem s..�er oara .o.,..M.�n. <br /> Ltis.aution n Cabrado <br /> Cartluus nufans — midrib and leaf <br /> usk thistle is designatmargins with <br /> - <br /> ,: ed as a"List B"species spines. <br /> ..R. .. in the Colorado Noxious <br /> with <br /> Weed Act. It is required to plumose <br /> t Mr'£` be eradicated;some popu- <br /> lations may be contained <br /> d bristles. <br /> or suppressed depending 3. Wide, Stout <br /> on state regulations. For lance-shaped <br /> management directions for bracts with <br /> each county, refer to the spiny tips. <br /> ,� " �.. .. �. most recent Rule,or visit <br /> <� www.colorado.gov/ag/co- <br /> weedcontacts weedcontacts for details. <br />