Strong, productive—and ruggedly individual. Whether one of a million in a forest or standing by itself on the savannah, a tree grows silently on its own, reaches its own heights, and ultimately dies alone. Right? Wrong. The aspen tree, it turns out, is not a solitary majesty, as I learned by sheer coincidence later that day from a friend who knows

Tree roots extend a long way, more than twice the spread of the crown. So the root systems of neighboring trees inevitably intersect and grow into one another—though there are always some exceptions. Even in a forest, there are loners, would-be hermits who want little to do with others.