Like many thistle species, carduus tenuiflorus
is not native to the US, originating in Europe and north Africa, but has been introduced to the Americas and is present in the West along the Pacific coast. The flower heads consist of a tight cluster of thin, tubular disc florets, pink or light purple, with bluish or dark purple anthers at the tips; below are many spiky, hairy, upwards-pointing phyllaries. There may be between 5 and 20 flower heads at the top of each stem. Both leaves and stems are very spiky. The plant is classed as a noxious weed in many areas.