Tall types look like something straight out of a fairy tale garden, while ground-hugging types are good in rock gardens, more formal gardens, and many other situations. Most are perennial, but a notable exception is Canterbury bells, a stately biennial (it takes two years to bloom).
Flowers come in blue, purple, white, or pink. The genus includes over 500 species and several subspecies, distributed across the temperate regions of the Northern Hemisphere, with the highest diversity in the Mediterranean region east to the Caucasus.
The species include annual, biennial and perennial plants, and vary in habit from dwarf arctic and alpine species under 5 cm high, to large temperate grassland and woodland species growing to 2 metres (6 ft. 7 in) tall.