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Magnolia is one of the most ancient angiosperm (flowering plant) genera, with fossil specimens dated at 20 million years old, and fossils of plants belonging to the Magnoliaceae family dating to 95 million years ago. The genus appears to have evolved before bees appeared, so the floral structure developed to encourage pollination by beetles, as described in this video on the southern magnolia, M. grandiflora (see YouTube clip).
Magnolias have large, aromatic flowers, usually bisexual (perfect), with 3 sepals and 6–12 petals (sepals and petals are not clearly differentiated, so are called tepals), with many stamens in a spiral. Flowers may be white, cream, yellow, pink, or purple. Flowers, borne on branch tips, have numerous simple ovaries in the center, which form a cone-like fruit with seeds (usually red) hanging from the center by slender stems. Leaves are alternate and entire (smooth-margined), and are tough, leathery, and evergreen in some species, but thin and deciduous in others. Leaves are quite large in some species, and are generally considered attractive, but lack fall color.
Eight species of Magnolia are native to the southeastern U.S., where they have become a popular symbol of southern culture, used in myriad place names and in literature, music (including magnolia-titled songs by the Grateful Dead, Beck, and JJ Cale), movies, and art. Magnolia is the state tree of Mississippi, and M. grandiflora (southern magnolia or sweet bay) is the state flower of both Mississippi and Louisiana.
Many magnolias are cultivated as garden ornamentals, and numerous cultivars and hybrids of North American and Asian species have been developed. Gardeners consider magnolia flowers to be of unsurpassed magnificence among temperate species—M. grandiflora has the largest flower of any North American species. In addition to their horticultural uses, a few magnolia species are used locally as timber sources, including M. acuminata, M. grandiflora, and M. virginiana in the southeastern U.S.
Popular North American species for garden use include M. grandiflora (laurel, southern magnolia, or sweet bay; M. virginiana (sweet bay); M. macrophylla (big-leaf magnolia); M. tripetala (umbrella tree); and M. acuminata (cucumber tree). Hybrids include Thompson’s magnolia (M. tripetala X virginiana).
Popular Asian species include M. liliflora or M. quinquipeta (lily magnolia); M. denudata and M. heptapeta (yulan magnolia); M. X soulangeana (saucer magnolia, a hybrid between lily and yulan magnolias); M. sieboldii (Oyama magnolia, the national tree of North Korea); and M. stellata (star magnolia). These Asian species range from small shrubs to tall trees, with flower colors ranging from white to pink to crimson to purple, and fruits with diverse colors.
Magnolias (in particular M. officials) have been used for medicinal purposes in China, for a tonic to treat neurosis and gastrointestinal disorders. Documents dating to 1083 record these uses, and extensive cutting of trees to make the tonic has led to declines of wild magnolia populations.
(Encyclopedia Britannica 1993, Everett 1981, Wikipedia 2011)