Byline: Christina Le Beau

Barbara Whitney Carr and Sophia Siskel tell slightly different stories about their first meeting in June 2005. But they agree that at some point, Ms. Siskel told Ms. Carr, then CEO of the Chicago Botanic Garden, she wanted her job.

"I'd never had anyone be quite so candid with me,'' says Ms. Carr, who was contemplating retirement and decided right then to mentor Ms. Siskel, who was "grounded and self-confident, someone who knew her own abilities but didn't push them.''

In February 2006, Ms. Siskel left the Field Museum to join the garden as vice-president of visitor programs and operations, and the grooming began. She took the reins from ...