If you are going hiking this week (or in late April-May some other year), be on the lookout for mulberry trees. Here in NW Arkansas, the berries were starting to be ripe last week and are now peaking. We've been raiding trees along various trails here in Fayetteville and it's been a lot of fun.
For more edible treats you can find outdoors visit this post.
2012 - Late April - May
2013 - Late May - June
2014 - I think we just missed them, but I'm guessing it was Late June. Very cool summer.
2015 - Mid-May - June (bumper crop!)