National Geographic : 2000 Oct
Waiting for Water Saguaro cactuses in the cooler uplands of Arizona's Superstition Mountains (right) prefer sunny, south-facing slopes. The north side offers more moisture, but winter frosts can kill seedlings. When rain comes, desert plants seize the moment. After a few well-timed storms, wildflowers fill what was once a dusty basin in Sonora's Pina cate Biosphere Reserve (above). I lingered for the color-green veins are mesquite trees and orange patches are blooming globe mallow -and for the uncom mon delight of flying through fragrant space.