JSTOR: The Introduction of Acacias into California: H. M. Butterfield. "Previous to 1849 there were no Acacias in California. ... [in 1858] California nuserymen were ... importing seeds directly from Austrailia."

[Wikipedia] Australia native: Acacia dealbata, the silver wattle, blue wattle[3] or mimosa,[4] is a species of flowering plant in the legume family Fabaceae, native to southeastern Australia in New South Wales, Victoria, Tasmania, and the Australian Capital Territory, and widely introduced in Mediterranean, warm temperate, and highland tropical landscapes. (contributed by Mary Ann Machi)

[Cal-IPC] Invasive: Acacia dealbata (silver wattle) is a tree (family Fabaceae) found in the coastal ranges, San Francisco Bay area, and south coast of California. It favors disturbed places in coastal prairies, riparian areas and coniferous forests. Silver wattle is often confused with green wattle (Acacia decurrens), but is distinguishable by the small, silvery hairs that grow on its twigs. It spreads via rhizomes and seeds, and easily resprouts after being cut. Acacia dealbata changes soil chemistry by fixing nitrogen, and the plants? fallen leaves may have allelopathic effects that prevent the growth of native understory plants. Like many Acacias, silver wattle is commonly planted as an ornamental. View the Jepson Herbarium video to help identify Acacia species. Cal-IPC Rating: Moderate (contributed by Mary Ann Machi)