A couple years ago, I planted a white nectarine tree. I don't recall how or why, but it didn't make it through the winter. The next growing season, I had a large, dead stick in my garden. I went ahead and pulled out that stick, planting a peach tree in its place.
To my surprise, a few feet from the original nectarine tree, another tree grew. Usually, I pull out volunteer trees, especially the damned sugar maples from the neighbor behind us. I let this one grow, curious if it would produce any fruits as tasty as its predecessor did. As I forgot to copper sulfate my stone fruits this year, the yield has been miserable (boo, peach leaf curl), but greater than zero.
Yes, greater than zero is one.
To my delight, a tasty "one." I'll be keeping the tree.