Yellow starthistle is an invasive species native to the Mediterranean region and Asia. It has flowers that resemble spotted knapweed. Starthistle spreads by seed and each flower can produce up to 150,000 seeds. These seeds can remain viable up to 12 years. When consumed, yellow starthistle is toxic to horses causing "chewing disease".
Roots: Taproot up to 6ft deep
Stem: Rigid, up to 5ft tall
Leaves: Grayish-green color and are covered with a cottony wool. Lower leaves are up to 3 inches long and deeply lobed, while upper leaves are short and narrow with fewer lobes and give the stems a “winged” appearance.
Flowers: bright yellow and sharp spines up to ¾ inches in length surround the base of the flower.
Prevention:This weed is only found in a few counties in Montana. If found contact the Weed District immediately.