An in-depth guide to a plant group prized for its vivid blue hue. Renowned for its stunning blue flowers, agapanthus--sometimes known as the blue lily or lily of the Nile--is a group of rhizomatous plants native to southern Africa. First cultivated in the Netherlands in the late seventeenth century, it rose to prominence as a conservatory plant in England during the eighteenth and nineteenth centuries after certain varieties were found to be hardy...