appearances arid Cacti cactus clumps clusters coloring colors colouring colours display edge edges flora frilled frills garden-display garden-plants green irregular leaves light ornamental perennials plants pointed protection ribbed ribbing ribs shape shapes sharp short-spikes small-spines spikes spines spiny succulents sunlight surface surfaces tall textures unusual variations variety various african distinctive greenery patch section shade texture colorful colourful barrel barrel-cactus round appearance bell-shaped biennials blooming blooms clump-forming colored coloured cultivars decorative Digitalis downward-facing erect exotics floral flower-spikes flowers foxglove garden garden-flowers herbaceous horticultural horticulture mottled nature petals potent-glycosides shaped tall-spikes toxic toxicity tubular whorls attract-prey attracted attraction carnivore carnivorous carnivorous-plants cover devour digest digested digesting enzymes funnel insect-trap insects nectar-like-secretions nutrient-source nutrients operculum passive-trap pitcher-plants pitchers pitfall-traps prey proteases rims slippery species trap vegetation veins