As I walked down a side path at Longwood Gardens in Kennett Square, Pennsylvania, on a bright, sunny day in June, two quite distinct sights converged just in front of me. One was a middle-aged foursome of fellow visitors, all clad in the near-mandatory style of the vacationing 1980s American: immaculate pastel sports clothes and bulbous white sneakers. The other sight was a spectacular tree, one whose branches, instead of ascending toward the heavens, droop mournfully down to the ground—what garden people call a weeping form. Suddenly a member of the foursome broke away from her companions, ducked between the sagging branches, and disappeared completely from view, rather like a chipmunk bolting into the shrubbery.