[Wikipedia] Origins: Carduus pycnocephalus, with common names including Italian thistle, Italian plumeless thistle, and Plymouth thistle, is a species of thistle. It is native to: the Mediterranean region in southern Europe, North Africa, and Western Asia; East Europe and the Caucasus; and the Indian Subcontinent. The plant has become an introduced species in other regions, and on other continents, often becoming a noxious weed or invasive species. (link added by Jessica Johnston)

[CNPS SLO] Introduction: A member of the Asteraceae family, Italian thistle is an annual herb native to the Mediterranean region and is widespread in California, Oregon and Washington, however it is not found east of the Sierra Nevada. It was accidentally introduced into United States (Batra et al. 1981) and California (Goeden 1974) in the 1930s. Robbins (1940) reports it as early as 1912 near Fort Bragg in Mendocino County. (link added by Jessica Johnston)