The scientific name comes from the Latin `onos` for donkey and refers to the supposed effect of causing flatulence in donkeys. (Make up your own common name!) An enormous biennial with rosettes to 6 feet wide and plants 6-12 feet tall. The leaves and stems are covered with white, cobwebby to felty hairs, and the stems have prominent, spiny wings. This species can grow in a great variety of soils and sites. The photos on page 225 of the California Growers Guide are actually bull thistle (Cirsium vulgare); however, the text on the back seems to be accurate for Scotch thistle.