I am looking to plant a few trees this year, they are not in a high priority location. I am mostly just doing it to keep my hill from eroding. I have heard ( i dont know how well documented this is) certain trees can provide different Health benefits? I was interested in this and was wondering if anyone had any information related to this.
It's an intriguing idea, but as far as I'm aware, not quite as you phrase it. Plane trees are renowned for tolerating polluted air and do a good job of sopping some of it up; Yew provides a toxin from which the drug tamoxifen, a cancer treatment, is derived, and of course, Willow was the original source of aspirin before it was synthesized, so in that sense, they can be healthy. I can't think of any other way they might be more healthy for humans in the vicinity though, other than the fact that all trees absorb and store carbon, taking in carbon dioxide and giving back oxygen to the atmosphere.
When you say tree with medicinal properties, the first one I can think of is the Neem tree. I dont know if it can grow in your country. But in large parts of Asia it grows easily & abundantly, with little or no care. All parts of the tree have medicinal value. Neem oil & other products are used widely especially in organic farming to control pestilence in plants.
You could take a look at this link http://en.wikipedia.org/wiki/Azadirachta_indica
Ginko biloba could be medicinal, but no one seems to agree on that... here is a good list from Washington State: http://www.wsdot.wa.gov/Environment/CulRes/ShrubsTrees.htm
not everything on that list is zone 5 ok, but things like the chokecherry would be.
the state tree of NH (Betula papyrifera) is used to make Birch Beer...