The classic eucalyptus conundrum

Is it true that the essential oils that eucalyptus exude prevent anything from growing beneath them?
  Some experts think not and it’s more likely that the roots gobble up nutrients and the canopies cast too much shade for smaller plants to thrive there, just like any grove of large trees would.
  In fact, San Marcos Growers posts an extensive list of plants that grow under eucalyptus.
  Could any of them look better than this scene from Sunset’s Fresh Dirt blog of Geranium madarense? All simply from reseeding—fabulous and free after you buy the first plant. Click the link to get the story. 
Photo: Rand Molnar.