According to Anne Orth Epple's book, PLANTS OF ARIZONA. ( LOC #94-78616 ). Optuntia violacera var. santa-rita. aka purple prickley pear, blue-blade, or dollar cactus.Color varies with drought or lower temps. Grows appx. 4000 ft or lower in elevation. 28 species of Optutia in AZ. Hope this helps. Book is available at state parks bookstores & I reccomend it highly. jg