How did Yellow starthistle get here?
Yellow starthistle, actually related to the knapweeds, began its new life in America sometime around 1849. It most likely came from its native Europe in shipments of alfalfa seed. Multiple introductions occurred, with the first of these in California. Road building, development, and expansion in the ranching industry contributed to the rapid and long-range establishment of new satellite populations. What are its characteristics? Fully mature, this winter annual forb stands about 3 feet tall and has yellow flowers and very spiny flower heads. As many as 10,000 seeds can be produced by each plant. These hitchhike by jabbing sharp spines into passing hide, clothing or tires. Once in the soil, these seeds can lie dormant for more than 10 years until conditions are right to sprout. A rosette forms in the fall or early spring and then a flowering stalk bolts in early summer. Dense stands develop that are nearly impossible to walk through because of their menacing spiked flower heads. Why is
