No not a Buddleia. Those are pretty amazing plants to attract butterflies and hummingbirds. I'm talking about Eupatorium coelestinum or Mist Flower.

I was at a great nursery in Austin called The Natural Gardener and took a stroll through their butterfly garden. Well down here it's still warm in November and the monarch butterflies are migrating through. This shrub doesn't have much of a scent and the blooms aren't that showy. But it is a butterfly magnet! I saw at least three species of butterflies feeding on it. At any given moment there were about 2 dozen butterflies on each of the three bushes. Nearby, the milkweed and lantana called out for the butterflies, but to no avail. They all went to the Mist Flower bushes. These are amazing little/big perennials that grow about 3-4 feet high and about 5-6 feet wide. They bloom late in the season around October for us but I'm sure that varies with climate. The thing to remember is "late season." I was told that there are a couple dwarf varieties as well which might be nice. These guys will self seed and naturalize in a bed, and that's great, but maybe you wouldn't want too many 4 feet plants crowding your beds.