C.ovata probably goes farther north than any other usefully edible member of the genus.
John Gordon offered a number of shagbark selections from his nursery in Amherst NY, but with his passing a few years back, I'm not aware of another U.S. nut tree nursery really catering to growers in areas colder than zone 5, unless SLN has a selection - and as ClarkinKS has alerted us, 2015 is SLN's last season.

Here is a link that might be useful: C.ovata

Hiking around Canadian Thanksgiving (2nd Monday in October) is a good time to collect the nuts around here. The natural populations just north and northeast of here would have experienced zone 4b many times since they were (likely) brought here by First Nations.

There are also naturalized populations just west of Georgian Bay (Lake Huron) and in the Lanark Highlands (2 hrs drive north of Kingston, Ontario), both rated zone 4a and both almost certainly established by First Nations people.

I can actually get them from some local retailers in the Twin Cities like Out Back Nursery, although I don't think they ship.

I got mine from Reeseville Ridge Nursery down near Madison, but you can also order them from http://www.wallace-woodstock.com/, which is near Black River Falls, WI and a SOLID zone 4a - maybe even borderline 3b.

I am sure there is a difference between NE and Midwest populations, but our hickories could certainly take your minimum temps - not sure if they would play nice with soil/humidity. I haven't even had any tip dieback even given last year's awful winter (although absolute minimums were only in the -20s)

Thanks for all the input.

I would browse "Oikos tree crops" website or hold out in case someone who has grown them, speaks up.

Never mind someone already spoke up.

I will be trying several Carya Ovata seeds, from zone 5 New York in my zone 6 yard. I have ordered 8 seeds from Ebay. I don't have enough experience though to say that my mentioning this won't be taken in the wronge context.

I have collected Carya ovata seeds a couple of times near where I work on NH's coast. However, apparently the nuts often aren't fertile, both from what I've read and from experience - none have sprouted even though I've handled them the same way I've handled walnuts with success.

It seems as though my drunken evil twin has been at it again, posting things that make no sense. Poaky1