Where do invasive plants come from?
They come from all over the world; giant reed (Arundo donax) from Europe, pampasgrass (Cortaderia selloana) from South America, bermudagrass (Cynodon dactylon) from South Africa, and tree of heaven (Ailanthus altissima) from China. Invasive plants have been both intentionally and unintentionally introduced into California. Unintentional introductions have typically arrived accidentally, for example; as contaminants in crop seed; in hay or forage; on machinery, equipment or vehicles; or in or on livestock. Examples of these weedy species are yellow star thistle (Centaurea solstitialis) and many other thistles, ripgut brome (Bromus diandrus), and common plantain (Plantago major). About half of the invasive plant species in California were intentional introductions for what was felt, at least at the time of introduction, to be beneficial purposes. Some species were planted extensively along streams for erosion control; these include pampasgrass and saltcedar (Tamarix ramosissima). Hottent
