Blackberry vines clog the empty lots and roadsides of the Pacific Northwest. When I moved here I thought they were a native feature. I enjoy the berry season, picking ’em for free on walks, eating ’em raw and making cobbler. On Wednesday as an Earth Day gesture, my co-workers and I spent half the day clearing blackberry thickets from alongside the Sammamish River. These blackberries that have taken over the region are actually not native. The Himalayan and evergreen blackberry were brought to the U.S. in the late 1800s to cultivate for fruit. The plants spread aggressively and are difficult to control. The canes reach rapidly over fences, even roofs. Any bit that touches the ground can take root and spread further. The dense tangle of branches block sunlight and choke other plants. After searching in our own yard a few years ago for the Mother Plant that all our blackberry vines branched from, I theorized that there is one true Mother Plant somewhere in the U.S., still sending out shoots.