appearance bell-shaped biennials blooming blooms clump-forming colored colorful colors coloured colourful colours cultivars decorative Digitalis display distinctive downward-facing erect exotics flora floral flower-spikes flowers foxglove garden garden-flowers garden-plants herbaceous horticultural horticulture light mottled nature ornamental perennials petals plants potent-glycosides shape shaped shapes tall-spikes textures toxic toxicity tubular unusual whorls attract-prey attracted attraction carnivore carnivorous carnivorous-plants clumps clusters coloring colouring cover devour digest digested digesting edge edges 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 variations variety vegetation veins