Also, they are on the edge of the "drip line" of an English walnut. After reading several articles on walnuts they make it sound like nothing besides grass and weeds will grow within 50' of a walnut.
After reading that I felt like running right outside and chopping the walnut down. Yet there are several pines planted as seedlings 7 years ago that are thriving under the walnut. It's hard to know what to believe.