I've been doing some deep digging on the web and have come up with some awesome sources for those living in PA and/or USDA zone 5A thru 6A. Most of this information comes courtesy of the Penn State Agriculture Extension.
First check your local college to see if they have an agriculture department, if so; chances are good that they have an "extension" and will have many articles and helpful resources for your region.
Now, on to the good stuff:
First up is a link to the Purdue University New Crop Resource page http://www.hort.purdue.edu/newcrop/default.html# Where they are dedicating this site to the restoration and use of heirloom and ancient/non-traditional agriculture fruits, veggies, nuts etc. - Includes the famine foods page with thousands upon thousands of non-traditional foods (Ie: perfect for permaculture perhaps?)
http://plants.usda.gov/java/altCrops?entry=initial State search that gives data/fact sheets about each plant available to grow in that state, sortable and searchable by over 20 different crop attributes. Click the "state search" link on the left side bar.
Even if some of the tree that you see are not listed for your zone, search for a regional vendor they will have a cold hardy one.
For example these upstate NY guys. http://www.sln.potsdam.ny.us/
Iterations are fine, we don't have to be perfect
Location: Pennsylvania Pocono Mt Neutral-Acidic Elv1024ft AYR41in Zone 5b
posted 6 years ago
S. Bengi Wow, St. Lawrence Nurseries is amazing. I just found several hard to find plants and it's a northern climate, local nursery to boot. Thank you!
posted 6 years ago
Thanks for the other sites, they are very good. Here is another I found this morning: www.wildflower.org - search, sort by perennial and then read about the plants to find lesser known potentials for your forest. Like the common pawpaw.