Magnolia is a large genus of about 210[a] flowering plant species in the subfamily Magnolioideae of the family Magnoliaceae. It is named after French botanist Pierre Magnol.
Magnolia is an ancient genus. Appearing before bees evolved, the flowers are theorized to have evolved to encourage pollination by beetles. To avoid damage from pollinating beetles, the carpels of Magnolia flowers are extremely tough. Fossilized specimens of M. acuminata have been found dating to 20 million years ago, and of plants identifiably belonging to the Magnoliaceae date to 95 million years ago. Another aspect of Magnolia considered to represent an ancestral state is that the flower bud is enclosed in a bract rather than in sepals; the perianth parts are undifferentiated and called tepals rather than distinct sepals and petals. Magnolia shares the tepal characteristic with several other flowering plants near the base of the flowering plant lineage such as Amborella and Nymphaea (as well as with many more recently derived plants such as Lilium).
The natural range of Magnolia species is a disjunct distribution, with a main center in east and southeast Asia and a secondary center in eastern North America, Central America, the West Indies, and some species in South America.
Magnolias are spreading, evergreen or deciduous trees or shrubs, characterised by large fragrant flowers which may be bowl-shaped or star-shaped, in shades of white, pink, purple, green or yellow. In deciduous species the blooms often appear before the leaves, in Spring. Cone-like fruits are often produced in Autumn.
As with all Magnoliaceae, the perianth is undifferentiated, with 9–15 tepals in 3 or more whorls. The flowers are bisexual with numerous adnate carpels and stamens are arranged in a spiral fashion on the elongated receptacle. The fruit dehisces along the dorsal sutures of the carpels. The pollen is monocolpate, and the embryo development is of the Polygonum type.
Taxonomists, including James E. Dandy in 1927, have long had an interest in observing fruits of Magnoliaceae and have often used the differences, or perceived differences, in fruit characters to justify systems for classification.
Star magnolia from botanical gardens, Halifax, Nova Scotia
In general, the genus Magnolia has attracted horticultural interest. Some, such as the shrub M. stellata (star magnolia) and the tree M. × soulangeana (saucer magnolia) flower quite early in the spring before the leaves open. Others flower in late spring or early summer, including M. virginiana (sweetbay magnolia) and M. grandiflora (southern magnolia).
Hybridisation has been immensely successful in combining the best aspects of different species to give plants which flower at an earlier age than the parent species, as well as having more impressive flowers. One of the most popular garden magnolias, M. × soulangeana, is a hybrid of M. liliiflora and M. denudata.
In the eastern United States, five native species are frequently in cultivation: M. acuminata (as a shade tree), M. grandiflora, M. virginiana, M. tripetala, and M. macrophylla. The last two species must be planted where high winds are not a frequent problem because of the large size of their leaves.
The flowers of many species are considered edible. In parts of England, the petals of M. grandiflora are pickled and used as a spicy condiment. In some Asian cuisines, the buds are pickled and used to flavor rice and scent tea. In Japan, the young leaves and flower buds of Magnolia hypoleuca are broiled and eaten as a vegetable. Older leaves are made into a powder and used as seasoning; dried, whole leaves are placed on a charcoal brazier and filled with miso, leeks, daikon, and shiitake, and broiled. There is a type of miso which is seasoned with magnolia, hoba miso.
In parts of Japan, the leaves of M. obovata are used for wrapping food and cooking dishes.
The bark and flower buds of M. officinalis have long been used in traditional Chinese medicine, where they are known as hou po (厚朴). In Japan, kōboku, M. obovata, has been used in a similar manner.
The cucumbertree, M. acuminata, grows to large size and is harvested as a timber tree in northeastern US forests. Its wood is sold as "yellow poplar" along with that of the tuliptree, Liriodendron tulipifera. The Fraser magnolia, M. fraseri, also attains enough size sometimes to be harvested, as well.
Magnolias are used as food plants by the larvae of some Lepidoptera species, including the giant leopard moth.
Chemical compounds and bioeffects
The aromatic bark contains magnolol, honokiol, 4-O-methylhonokiol, and obovatol. Magnolol and honokiol activate the nuclear receptor peroxisome proliferator-activated receptor gamma.