Hydrangeas, poppies, lady's slippers, lilies, and geraniums – the rich bounty of plant hunters transformed European gardens into blooming paradises and brought exotic species into greenhouses and conservatories. Without these treasures, our windowsills and balconies would look dreary. Who were these men and women who gave up comfortable lives to scour unexplored regions beyond the oceans, risking their lives and enduring great hardships to discover new plants? The two authors here paint colorful portraits of great plant hunters who set out to harvest "green gold." They reveal little-known facts: that the scholar Alexander von Humboldt, to whom we owe the dahlias, sent home more than 6,000 plants from South America. Or that the poet Adelbert von Chamisso found the seeds of California poppies. The ophthalmologist Franz von Siebold...