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Musk Thistle Identification and Management plumose bristles that appear barbed un- W- der magnification. Musk thistle produces - t many flower heads.The tallest shoots flower first;lateral shoots develop in leaf { axils.A robust plant may produce 100 or ' _=r more flowering heads. Reproduction is usually via out-crossing through insect ' r� = j pollination, but self-pollination also , { occurs. Flowers emerge in May through September.Seeds develop shortly after _____-- flowers emerge. Flower buds can contain viable seeds from self-pollination.Seeds can mature on severed bud and flower- , ^ heads.Seeds remain viable in the soil for up to about 14 years.Seeds can germi- k. r" Hate and emerge from spring through "�'=!,'Musk thistle Carduus nutans L.is a fall. non-native biennial forb that re- _ produces solely by seed. During the first usk thistle habitat is found in a year of growth,a rosette forms in spring M variety of environments extend- or fall. During the second year in mid to ing from shortgrass prairie to alpine. late spring,the stem bolts,flowers,sets e seed,and the plant dies. It is strongly associated with heavily „t disturbed sites,where over-use occurs or where site conditions are poor due Musk thistle can grow up to 6 feet to land management practices.This �- tall.The leaves have spines,are includes over-grazed areas, large fires, waxy,and dark green in color with a trails,ditches and roadsides. Infested LA prominent light green to white midrib � ^^ livestock pasturs suffer that can be seen from a distance.Leaves from significantly � decreased carrying capacity. are dentately lobed;leaf bases some- times extend down below the point of S.1 attachment.The terminal flower heads ecause musk thistle reproduces C� the key for suc are purple, large in size(1.5 to 3 inches Bsolely from seed, in diameter) and bend over as if nod- cessful management is to prevent seed = 4 r production.Once flowers emerge and #Ir `A`•, ding.These flower heads are made up of start to produce seed,effective manage- only disk flowers.They are surroundedi.`s by numerous,wide and stout lance- ment options will become limited.Once shaped,spine-tipped bracts that resem- sites are infested, musk thistle can form A D ble an open pineapple.The pappus has dense stands. Prevention,adjusting land management practices,a robust inte- 2015 Quarter Quad Survey grated treatment plan and , Points restoration are critical to Key I -- -----""-----"" -- eliminating this species. Musk Thistle1. Leaf with white asm,.,ma m ca°,aa° nr. midrib and leaf �., usk thistle is designatwith - "° M ed as a"List B"species spmarginsines. in the Colorado Noxious u, t Weed Act.It is required to 2. Pappus" 1 be eradicated;some popu- plumose lations may be contained barbed .•�• or suppressed depending 3.Wide, stout on state regulations. For lance-shaped _ - management directions for i bracts �. each county, refer to the spiny tips. • _ �• most recent Rule,or visit www.colorado.gov/aci/co- weedcontacts weedcontacts for details.