Ginny, the first place I thought of was Cricket Hill Garden in CT, but it's probably more like 2 1/2hrs from Boston. I've never been there for their peony festival but I would imagine they have many varieties and I would assume labeled.

I'd like to know as well what else is around so hopefully some other folks will reply.

Here is a link that might be useful: Cricket Hill Garden

There is a Peony Garden in Cumberland Foreside, Maine just off of Route 1 and Tuttle Road. It is north of Portland, Maine about 20 minutes making it about 2 hours north of Boston. You should check the internet for Peony Garden Cumberland Foreside, Maine to get a phone number as the sign out front says "by appointment". I confess to having driven up to the garden uninvited to have my lunch in their parking lot....very scenic.