I wouldn't necessarily think of attracting butterflies to a shade garden - but was pleased beyond belief two years ago, when I found these lovely monarch butterflies crawling all over my Ligularia dentata.
Ligularia is a big beefy plant that needs quite a bit of moisture. It is about a meter and a half high and a meter wide when in bloom. This seedling, from an original plant I'd purchased, has lost the characteristic dark burgundy colour on the underside of the leaves and stems, but seems to be far more tolerant of the sandy dry soil it is growing in.
Ligularia blooms at the end of August, beginning of September for me - so its blooms are timed perfectly to attract these migrating butterflies. You might also be pleased to know, that it has very attractive seed heads, and of course, with seed heads you'll have lots of plants to share with friends in the neighbourhood - so they too can enjoy these beautiful butterflies in their shade gardens.