This is a double flowered perennial morning glory, Convolvulus hederacea flore pleno, a nice looking form of a rather weedy plant. I got my plant from Arrowhead alpines some years ago and it has done well, sometimes too well. Like the single flowered bindweeds it is cousin to, it spreads underground by means of long rhizomes, and if any piece is left behind when digging them up, it will come back as a plant. Still, I really do enjoy the beautiful flowers, and the vines must compete with other vigorous plants in a sunny but difficult spot. I'd say the thing I least like about it is that the foliage gets fairly ratty as summer goes on, since various bugs/slugs like to chew on it. If any vines appear to be overtaking any less tough neighbors, I merely pull them out, so that even though they will come back, the other plants have time to grow without serious competition for a while. It does not set seed, so its wandering is limited to the spot is is planted in, which is a good thing.