these plants are perennial herbs, often with thick, fleshy roots. the stem usually grows erect from a caudex. there are usually several basal leaves borne on long petioles. the leaves on the stem are alternately arranged in most species. flowers are solitary or borne in cymes. the corolla of the flower is bell-shaped, funnel-shaped, or tubular, with five lobes. the corollas of most species are blue. there is a characteristic nectar disc at the base of the stamens.