arid barrel barrel cactus Cacti cactus clumps clusters coloring colors colouring colours compact covered echinocactus globose globular perennial pointed points pronounced ribs protective pups ribs round shape shaped sharp skin soft-wooded perennial spikes spination spines spiny surface symmetrical symmetry thick tough skin to-the-point cream flower garden Kniphofia natural nature petal spike stem summer tube yellow autumn bloom dahlia flowering plant orange petals pink plant peach blue border England geranium Great Britain many bright cultivar flowers lupin lupinus purple red showy white Aruncus bush feathery frond