[Cal-IPC] Invasive: Centaurea melitensis (Malta starthistle, tocalote) is a bushy annual (family Asteraceae) found throughout most of California and in many other western states. Malta starthistle prefers disturbed and open areas, including grasslands, open woodlands, agricultural fields and roadsides. It is most invasive in California's central western and southwestern regions. While Malta starthistle is less invasive than yellow starthistle (Centaurea solstitialis), it still spreads quickly by producing great quantities of seed if given the proper conditions. Insects such as the false peacock fly (Chaetorellia succinea) and hairy weevil (Eustenopus villosus) have been used as biological controls with some success. Cal-IPC Rating: Moderate (link added by Mary Ann Machi)

[Wikipedia] Europe & Africa native: This plant is native to the Mediterranean region of Europe and Africa. It was introduced to North America in the 18th century; the first documented occurrence in California is in the adobe of a building constructed in San Fernando in 1797. It is also naturalized on a number of Pacific islands. (link added by Mary Ann Machi)