Floris van Breugel / Barrel cacti (Ferocactus pilosus) and Ocotillo overlook Palm oasis at sunrise, Anza-Borrego Desert State Park, California, USA March

Jack Dykinga / Close-up of two Barrel cacti (Ferocactus acanthodes) in the eastern Chihuahuan Desert, Mexico

John Cancalosi / Fishhook barrel cactus (Ferocactus wislizeni) flowering. Arizona.

John Cancalosi / Fishhook barrel cactus (Ferocactus wislizeni) flowering. Arizona.

John Cancalosi / Fishhook barrel cactus (Ferocactus wislizeni), two flowers with bee pollinating. Arizona.

John Cancalosi / Fishhook barrel cactus (Ferocactus wislizeni) flowering besides Prickly pear (Opuntia sp), in desert. Arizona.

Tim Fitzharris / Saguaro (Carnegiea gigantea) and barrel cacti, Santa Catalina Mountains, Arizona

Cyril Ruoso / Fishhook barrel cactus (Ferocactus wislizeni) flower, Vizcaino Desert, Baja California, Mexico, May.

Cyril Ruoso / Fishhook barrel cactus (Ferocactus wislizeni) close up of flower, Vizcaino Desert, Baja California, Mexico, May.

Cyril Ruoso / Fishhook barrel cactus (Ferocactus wislizeni) close up of spines, Vizcaino Desert, Baja California, Mexico, May.

Cyril Ruoso / Fishhook barrel cactus (Ferocactus wislizeni) in flower, Vizcaino Desert, Baja California, Mexico, May.

Cyril Ruoso / Fishhook barrel cactus (Ferocactus wislizeni) in flower, Vizcaino Desert, Baja California, Mexico, May.