I'm about to put in a couple of Tangerine Beauty Crossvines, which are supposed to be wonderful in our Texas soil and climate. A new Texas Superstar plant from TAMU Agrilife. Allegedly, these are NOT invasive, while the related Trumpetvines are very much so. But they do produce seeds in the fall that seem to need no treatment to germinate. If those seeds fall, you'd think they'd root, and spread. How is it that they're not invasive?