Lilacs are prevalent in most areas on Cape Cod. They also seem to be pretty resilient (at least in my yard). When I bought my house a few years ago, we had to clear bunches of lilacs that had become choked with bittersweet. We dug them out with an excavator so we could get rid of all the bittersweet roots underneath. Some of the bittersweet was as big around as my arm. The lilacs seem to be coming back strong in these areas.