One of the reasons I used the term legacy plants, when working on what species might naturalize in gardens, was to avoid the use of the word invasive. As several members have pointed out, not all species are aggressive in all gardens. Behavior can vary within 50 to 100 miles. So, as also pointed out, knowing where a member gardens, and the climate, and specific growing conditions that trigger ebullient growth, to pick a different phrase, will help all of us make decisions for our own gardens. Kathleen Pacific Northwest, zone 7-8, mostly wet winters, though it is snowing right now, mostly dry mild summers