Cirsium douglasii is a species of thistle known by the common names Douglas' thistle and California swamp thistle. It is native to the central coast and northern California ranges, foothills, and plateaus, and adjacent parts of southern Oregon and northwest Nevada. It grows in wet places in a number of types of habitat. This native thistle, Cirsium douglasii, is a biennial or short-lived perennial herb growing up to 2. 5 metres (8. 2 ft) tall, with a branching woolly stem. The longest gray-tomentose leaves, located about the base of the plant, are up to 1 metre (3. 3 ft) long. They are sometimes lobed or toothed and are borne on a spiny petiole. The inflorescence is a cluster of several flower heads surrounded by small leaves. Each flower head is up to 3 centimetres (1. 2 in) long and lined with purple-tipped spiny phyllaries. The head contains purple or white flowers. The fruit is a dark-colored achene 2-4. 5 millimetres (0. 079-0. 177 in) long/diameter with a pappus which may reach 2 centimetres (0. 79 in) in length. VarietiesCirsium douglasii var. breweri (A. Gray) D. J. Keil & C. E. Turner - California, Oregon, NevadaCirsium douglasii var. douglasii - California