I ended up buying some native Pawpaw, but I think your native Pawpaw is different than mine.

I have found that Zebra STs love those small Pawpaw trees. Mine also grow very slowly.

What type of nectar plants do you have? They have short proboscis so they need flowers that don't have long tubes. I've seen them nectaring butterfly bushes and Vitex.

Here is a link that might be useful: Zebra Swallowtail Eurytides marcellus

I have purchased native paw paws also. They still grow very, very slowly. I have all sorts of nectar plants, including Vitex which is now blooming and buddleas which bloom pretty much all the time. The one nectar plant that I have many of is the large red penta. In my area any butterfly that uses nectar will use the pentas.

Thanks for the link. Some good information.

How far away from the park is your garden? Zebra STs form colonies near the Pawpaw. I've noticed that some times they branch out from that colony and will be seen other places that Pawpaw doesn't grow. At my other house, it took me 5 years to attract them.