Biological data source of trees
The Ecological Data Wiki search for Woody Plants is a good start for some nice datasets. There is also the USDA Plants Database which has information for every plant in the U.S. Woody species are well represented with lots of species specific info. These can be downloaded handily with an R package.  

Looking for occurrences? Put the species name into GBIF to get historical records of where and when a species was found. This has an R package as well.   

Want distribution maps for all trees in North America? Someone has done that for you here.  

Phenology? The National Phenology Network.

Edibility? I've never come across a specific data source for this. But the best reference I've used is the Handbook of Edible and Poisonous Plants of Western North America. It's an amazing book with years of research put into it. It does not have any pictures nor a key to identify plants, but it does have information on pretty much every plant in the Western U.S. at least at the genus level.