perennial, climbing, nitrogen fixers that don't choke trees

Well, title pretty much sums it up.
That's what I'm looking for.

Bonus points if they're:
-cold hardy
-edible or at least fodder for something you'd raise
-pretty
-you have direct experience with them on trees

I'm getting together some comprehensive information on tree guilds. Fruit tree, nut tree, lumber, etc. We have a TON of small time abandoned orchards in my area and I'm hoping this information will help in rehabilitating them.
I'm also hoping to get a lot of the info slimmed down into a pamphlet or printout I can give out to people interested in permaculture.

I think a pretty, edible garden underneath a fruit tree is the kind of accessible, suburban-friendly thing that could serve as a great entry point into the permaculture world for a lot of people.

Here are some perennial nitrogen fixing climbers that are hardy to zone 11: Lord Arison's Peas, Jicama, and the Lima Bean.

Here are some perennial nitrogen fixing climbers with high edibility ratings: Kudzu Vine, Jicama, Hyacinth Bean, and Hog Peanut. <---these ones are less hardy (up to zone 9), except for the jicama

These plants were found using the Plants For a Future Database.

Thanks, that link is a great resource

Groundnut is a hardy N fixing vine. It has an edible underground nut and attractive pea like blossom. Im growing it here in Idaho and it doesn't really seem like it would really strangle a tree like some other vines might. I posted some more info on groundnut here: http://traditionalcatholichomestead.com/2015/05/16/homestead-heros-plants-of-promise-ground-nut-strawberry/