Any variety of false indigo (baptisia australis) will provide food for some species of sulphurs and blues. This species is hardy to zone 3.

I have Baptisia australis here and a few years ago was looking up the various types of butterflies that it hosts and have the information in an Excel file. I don't know if these types of butterflies would be found where you live or not. Here is the list of butterflies that lay their eggs on B. australis:

Clouded Sulphur

Eastern Tailed Blue

Frosted Elfin

Hoary Edge

Orange Sulphur

Wild Indigo Duskywing

Out of that list, I've only ever seen and raised Clouded Sulphurs and Wild Indigo Duskywings here. B.australis grows to be a bush and has beautiful flowers that bloom several weeks and gets beautiful black pods when it goes to seed. Not many of these bushes are needed to provide plenty of food for butterfly larvae. I don't have any other kinds of australis.

Thanks so I should get one is what your saying?

Sure, I would if I were you. I didn't save any seeds last year or I'd send you some. If you do start one from seed, though, the plant won't bloom until its third year. So one started from seed this year won't bloom until 2017. I think that the Baptisia flowers are absolutely beautiful even if they only do bloom a few weeks like most other perennials..