Bradford Pear's Thorny Legacy: How "Sterile" Trees Became Invasive

'Bradford' Callery pear was planted everywhere for its flowers, fall color, and "sterile" fruit. But weak branch angles caused storm breakage, leading to bans. Newer cultivars ('Aristocrat', 'Cleveland Select') had better structure—but they cross-pollinated with 'Bradford' and each other. Birds spread the resulting fertile seeds by the thousands into natural areas.

Now Callery pear is a recognized invasive threat. The lesson: ecological consequences unfold over decades. What we "know" today may be wrong tomorrow. As Kim Todd wrote, nature "will continue to rattle, buck, elude, and astonish us."