lily, (genus Lilium), genus of 80 to 100 species of herbaceous flowering plants of the family Liliaceae, native to temperate areas of the Northern Hemisphere. Many lilies are prized as ornamental plants, and they have been extensively hybridized.
The word lily is also used in the common names of many plants of other genera that resemble true lilies. These include the daylily (Hemerocallis) and various species of the family Amaryllidaceae
The true lilies are erect perennial plants with leafy stems, scaly bulbs, usually narrow leaves, and solitary or clustered flowers. The flowers consist of six petal-like segments, which may form the shape of a trumpet, with a more or less elongated tube, as in the Madonna lily (Lilium candidum) and Easter lily (L. longiflorum). Alternatively, the segments may be reflexed (curved back) to form a turban shape, as in the Turk’s cap lily (L. martagon), or they may be less strongly reflexed and form an open cup or bowl shape, as in the wood lily (L. philadelphicum) and goldband lily (L. auratum). The flowers of some species are quite fragrant, and they occur in a wide variety of colours. Plants of most species range in height from 30 to 120 cm (1 to 4 feet); plants of certain species, however, exceed 2.5 metres (8 feet) in height.