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Global Range: The origins of Silybum marianum lie in the region of Southern Europe, the Mediterranean and Northern Africa. Its current distribution includes most temperate areas of the world. It is common in the Western U.S. as a weed afflicting pastures, wastelands and irrigation banks (Parsons 1973). It is believed to have been introduced in cattle feed.
Silybum marianum spread through both the southern and northern Central Valley of California during the 1940s, demonstrating a remarkable adaptation for colonizing. "The agricultural environment that was invaded had been dominated by alien weeds for 180 years. For a species without vegetative propagation to invade a community of annuals underscores the competitive advantage of its germination characteristics" Young et al. 1978). It is now common in both coastal and inland valleys.