Jack Dykinga / Saguaro cactus (Carnegiea gigantea) with twisted arms at sunset, with Ajo Mountains in the background, Arizona, USA.

Jack Dykinga / Organ Pipe Cactus (Stenocereus thurberi) amongst flowering Brittlebush (Encelia farinosa) and Teddy Bear Cholla (Opuntia bigelovii), with the Ajo Mountains in the background Organ Pipe Cactus National...

Jack Dykinga / Flowering desert lilies (Hesperocallis undulata) and desert golds (Geraea canescens) in the sandy flats beneath the Calumet Mountains. Mojave Trails National Monument, Mojave Desert, California, USA....

Tim Fitzharris / Saguaro (Carnegiea gigantea) cacti, Ajo Mountains, Organ Pipe Cactus National Monument, Arizona

Jouan Rius / Organ pipe cactus (Stenocereus thurberi) with the Ajo Mountains in the background, Organ Pipe Cactus National Monument, Sonora Desert, Arizona, USA

Tim Fitzharris / Organ Pipe Cactus (Stenocereus thurberi), Ajo Mountains, Organ Pipe Cactus National Monument, Arizona

Tim Fitzharris / Cactii in desert, Ajo Mountains, Organ Pipe Cactus National Monument, Arizona

Tim Fitzharris / Senita Cactus (Pachycereus schottii) group, Ajo Mountains, Organ Pipe Cactus National Monument, Arizona

Philippe Clement / Teddybear Cholla {Opuntia / Cylindropuntia bigelovii} in front of the Ajo Mountain Range, Organ Pipe National Monument, Arizona, USA May 2007

Tim Fitzharris / Saguaro (Carnegiea gigantea) and Ajo Mountains, Organ Pipe Cactus National Monument, Arizona

Tim Fitzharris / Saguaro (Carnegiea gigantea) and Teddybear Cholla (Cylindropuntia bigelovii) amid flowering Lupine and California Brittlebush (Encelia californica), Arizona

Tim Fitzharris / Ajo Mountains, Organ Pipe Cactus National Monument, Sonoran Desert, Arizona