Magnolia is a large genus of flowering trees and shrubs in the family Magnoliaceae, comprising between 210 and 360 or more species depending on the taxonomic treatment followed. The genus is named after the French botanist Pierre Magnol (1638-1715), with the name first coined by Charles Plumier in 1703 and formally adopted by Carl Linnaeus in his Species Plantarum of 1753.
Members of the genus are found across two widely separated regions of the world: a primary centre of diversity in east, south, and southeast Asia, and a secondary centre encompassing eastern North America, Central America, the West Indies, and parts of South America. Both deciduous and evergreen species occur, ranging in stature from compact multi-stemmed shrubs to large canopy trees exceeding 20 metres.
Magnolias are among the most ancient of flowering plants, and their flowers are believed to have evolved to attract beetle pollinators before bees arose. The blooms bear 9-15 tepals arranged in three or more whorls, often in shades of white, pink, purple, yellow, or green, and are frequently large and fragrant. The flower structure — with numerous spirally arranged stamens and carpels fused to the receptacle — is considered an ancestral floral plan. Fruits are cone-like aggregate structures bearing seeds with brightly coloured coats.
In cultivation, magnolias are prized as ornamental specimen trees and shrubs. They prefer fertile, moist, well-drained, and generally acidic soils, with most species best suited to USDA hardiness zones 5-9. Hybridisation between species has produced a wide range of garden-worthy cultivars, notably the saucer magnolia (Magnolia x soulangeana) and the star magnolia (M. stellata), which are among the most widely planted flowering trees in temperate gardens worldwide.
Etymology
The genus name Magnolia was first used in 1703 by the French botanist Charles Plumier, who dedicated it to his compatriot Pierre Magnol (1638-1715), a pioneering botanist and director of the Montpellier botanic garden. Carl Linnaeus formally adopted the name in 1735 and used it in his Species Plantarum (1753), where he initially treated the genus as monotypic, with Magnolia virginiana as the sole species.
Distribution
Magnolia has a markedly disjunct global distribution. The primary centre of diversity lies in east, south, and southeast Asia, encompassing China, Japan, Korea, the Himalayan region, and mainland and island Southeast Asia. A secondary centre covers eastern North America (where six species are native in states such as North Carolina), as well as Central America, the West Indies, and parts of South America.
Ecology
Magnolia flowers are interpreted as an early-evolved floral type: the large, robust tepals and the spiral arrangement of numerous stamens and carpels are thought to represent adaptations to beetle pollination, predating the diversification of bees. The hermaphroditic flowers bear 9-15 tepals in three or more whorls and produce cone-like aggregate fruits with seeds displaying brightly coloured coats that attract bird dispersers.
In landscape contexts, magnolias are appropriate for pollinator gardens and naturalized woodland settings. They are susceptible to magnolia scale, yellow poplar weevil, sooty mould, and Verticillium wilt, and are occasionally browsed by white-tailed deer. Chlorosis can develop in high-pH (alkaline) soils.
Cultivation
Magnolias thrive in fertile, moist, well-drained soils with a mildly to moderately acidic pH; they perform poorly in dry, infertile, or alkaline conditions. Most species do best in full sun, though smaller species and some cultivars tolerate partial shade. The typical hardiness range is USDA zones 5a-8b, though individual species vary considerably; hard frosts can damage stems and reduce flowering, and plants should be sited in sheltered positions away from cold, exposed aspects.
Plants range from 8-40 feet (2.5-12 m) tall, depending on species. Fleshy roots make transplanting sensitive — moving established specimens should be avoided. Pruning should be kept to a minimum because magnolias can be slow to recover from wounds. Many evergreen species carry richly scented lemon-vanilla flowers. Numerous cultivars have received the RHS Award of Garden Merit, including 'Leonard Messel', 'Susan', and 'Royal Star'.
Propagation
Seeds should ideally be sown fresh immediately after harvest; cold-stored seed can be sown in a cold frame in late winter. Germination is slow and irregular, extending from spring across up to 18 months. Layering in early spring is a reliable vegetative method. Some vigorous species are used as rootstocks for grafting less vigorous ones. Cuttings are also practised for selected cultivars.
Cultural Uses
The bark of Magnolia officinalis has been used for centuries in traditional Chinese medicine, where it is known as hou po. The bark contains the bioactive compounds magnolol and honokiol, and preparations have been prescribed as a stimulant, tonic, laxative, and anti-spasmodic. In North American folk medicine, bark of M. acuminata was used as an antiperiodic (historically as a substitute for quinine in treating malaria), as a digestive aid, and topically for toothache.
Culinary uses include pickling magnolia petals in the English tradition and using young leaves and flower buds in Japanese cooking. The fine-grained, relatively soft wood of some species is used for boxes, crates, flooring, and cabinetry. Culturally, Magnolia grandiflora is the state flower of both Mississippi and Louisiana and is a widely recognised symbol of the American South.
Taxonomy Notes
Magnolia is placed in the family Magnoliaceae, order Magnoliales, class Magnoliopsida. The GBIF backbone taxonomy records the accepted name as Magnolia Plum. ex L., published in 1753, and includes 591 descendant taxa across all ranks. Species counts vary considerably by authority, ranging from approximately 210 to over 360 accepted species depending on whether segregate genera such as Michelia, Talauma, and Yulania are subsumed.
Modern molecular phylogenetic studies have shown that Michelia and Magnolia subgenus Yulania are more closely related to each other than either is to the rest of Magnolia in the traditional sense, leading some authorities to merge these lineages and others to maintain them separately. This ongoing circumscription debate means that species counts and subgeneric assignments differ among global checklists.
