Cactaceae cactus desert flower Nyberg pental pentals plant cactii dry petal prickle sharp spike spine spiny water Echinocactus grusoni Golden Ball Golden Barrel Cactus Mother-in-Law's Cush thorns yellow agriculture background beautiful botanical botany close-up closeup color danger detail edible flora food green guest hurt indica leaf nature needle opuntia pain prick Prickly prickly-pear snail spiky succulent texture thorn thorny vegetable