For my zone, what plants would be best to attract and host butterflies?
That's a huge question, and you'd probably get more information by searching for a group in your geographic area who can guide you, or finding some of the many online sources of information.
That being said, you can't go wrong with any of the various Milkweeds (Asclepias tuberosa, A. incarnata, A. syriaca, A. purpurescens, etc.) to host Monarch cats and provide nectar for many beneficial insects. Dill, fennel, and parsley are easy to grow and host the Black Swallowtail cats. Beyong that, many of the native flowering plants will attract various butterflies to nectar.
Hope that helps.
Thank you so much! :)
...if you are in an area with Monarchs. Rather than asking your question based on hardiness zone, use the closest major city.
Zone 6 covers a lot of different climates, gardens there will vary.
The below link will give you some general ideas.
What I suggest is buying a butterfly book specific to your state, finding which butterflies are in your area, and then planting native hostplants for the butterflies you wish to attract. Also plant flowers to keep the adults fed. A water feature that is butterfly friendly also helps.
Like Larry said, if you give us a better idea of where you are, we will give you targeted suggestions but we might leave off something that you would want. Where I live, I figure I can attract 50+ butterflies. No one here is going to take the time to tell me which 50+ those are. Taking the time to do your own research might land you a cool butterfly or caterpillar that none of us has raised. I bought a bunch of new plants this year in hopes of raising some butterflies that are new to me.
Here is a link that might be useful: top ten butterfly magnets