My family owns a small property near Franklin in western North Carolina which has five healthy, mature black walnut trees. Their collective potential production is presently over 3,000 walnuts and the productive trees are over 50 years of age each.
These black walnut trees are of natural origin, very much alive and living near a creek ecology with perfect growing conditions and extra fertilizaton from the yard. There are young trees to take their place and old trees that are losing their battle for life and productivity. Still, there are enough black walnuts in line to grow nuts through the lifetime of my children.
Here is how I harvest those black walnuts...
Husked Black Walnut Seed - Photo by Steve Nix, Licensed to About.com