Bermudagrass Johnsongrass Medusahead Quackgrass Field Bindweed Hoary Cress Diffuse Knapweed Russian Knapweed Spotted Knapweed Squarrose Knapweed Purple Loosestrife Perennial Pepperweed Leafy Spurge Yellow Starthsitle Canada Thistle Musk Thistle Scotch Thistle Dyer's Woad Back to main weeds page   Scotch Thistle Onopordum acanthium   Rosette First year rosettes are 5 to 12 inches across. Second year rosettes may be four feet wide. Large spiny leaves up to two feet long and one foot wide are covered with dense hair, giving a grayish blue-green coloration. Adult This biennial plant commonly grows three to eight feet tall, but it may grow as high as 12 feet. Flower The flowers are violet to reddish with spine tipped bracts, blooming in mid summer. Weed Infestation Scotch thistle is native to Europe and eastern Asia. It grows well in waste areas, pastures, range land, and along canal and stream banks. Winged stems Stems are heavily ridged and very spiny. Back to main weeds page   Buffalobur Common Burdock Camelthorn Goatsrue Jointed Goatgrass Poison Hemlock Black Henbane Houndstongue Blue-Flowering Lettuce Western Whorled Milkweed Silverleaf Nightshade Yellow Nutsedge Puncturevine Russian-Olive Saltcedar St. Johnswort Bull Thistle Dalmatian Toadflax Yellow Toadflax Velvetleaf