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Magnolia grandiflora, commonly known as the southern magnolia or bull bay, is a tree of the family Magnoliaceae native to the southeastern United States, from Virginia south to central Florida, and west to eastern Texas and Oklahoma. Reaching 27.5 m (90 ft) in height, it is a large striking evergreen tree with large dark green leaves and large white fragrant flowers. Widely cultivated around the world, over a hundred cultivars have been bred and marketed commercially. The timber is hard and heavy, and has been used commercially to make furniture, pallets, and veneer.

Description

Magnolia grandiflora is a medium to large evergreen tree which may grow 27.5 m (90 ft) tall.[1] It typically has a single stem (or trunk) and a pyramidal shape.[2] The leaves are simple and broadly ovate, 12–20 cm (5–8 in) long and 6–12 cm (2–5 in) broad,[2] with smooth margins. They are dark green, stiff and leathery, and often scurfy underneath with yellow-brown pubescence. The large, showy, lemon citronella-scented flowers are white, up to 30 cm (12 in) across and fragrant, with 6–12 petals with a waxy texture, emerging from the tips of twigs on mature trees in late spring. Flowering is followed by the rose-coloured fruit, ovoid and 7.5–10 cm (3–4 in) long and 3–5 cm (1.5–2 in) wide.[3]

Exceptionally large trees recorded include a 35 m (114 ft) high specimen from the Chickasawhay District, De Soto National Forest in Mississippi which measured 17 feet 8 inches in circumference at breast height, from 1961, and a 30 m (99 ft) tall tree from Baton Rouge in Louisiana which reached 18 feet in circumference at breast height.[3]

Taxonomy

Magnolia grandiflora was one of the many species first described by Linnaeus in his Systema Naturae in 1759, basing his description on the earlier notes of Miller. He did not select a type specimen. Its specific epithet is derived from the Latin words grandis “big”, and flor- “flower”.[4]

Magnolia grandiflora is most commonly known as Southern magnolia, a name derived from its range in the Southern United States. Many broadleaved evergreen trees are known as bays for their resemblance to the leaves of the red bay (Persea borbonia), with this species known as the bull bay for its huge size or alternately because cattle have been reported eating its leaves. Laurel magnolia,[4] evergreen magnolia,[3] large-flower magnolia or big laurel are alternate names.[5] The timber is known simply as magnolia.[3]

 

Distribution and habitat

Magnolia grandiflora is native to the southeastern United States, from Virginia south to central Florida, and then west to eastern Texas and Oklahoma. It is found on the edges of bodies of water and swamps, in association with sweetgum (Liquidambar styraciflua), water oak (Quercus nigra), and black tupelo (Nyssa sylvatica). In more sheltered habitats, it grows as a large tree, but can be a low shrub when found on coastal dunes.[6] It is killed by summer fires, and is missing from habitats that undergo regular burning.[7] In Florida it is found in a number of different ecological areas that are typically shady and have well draining soils, it is also found in hummocks, along ravines, on slopes, and wooded floodplains.[8] Despite preferring sites with increased moisture, it does not tolerate inundation.[3] It grows on sand-hills in maritime forests, where it is found growing with live oaks and saw palmetto.[7] In the eastern United States it has become an escape, and has become naturalized in the tidewater area of Virginia and locally in other areas outside of its historically natural range.[9]

 

 

 

Ecology

Magnolia grandiflora can produce seed by 10 years of age, although peak seed production is achieved closer to 25 years of age. Around 50% of seed can germinate, and is spread by birds and mammals.[3] Squirrels, opossums, quail, and turkey are known to eat the seeds.[10]

 

 

 

 

 

 

 

Cultivation and uses

The plant collector Mark Catesby, the first in North America, brought Magnolia grandiflora to Britain in 1726, where it entered cultivation and overshadowed M. virginiana which had been collected a few years earlier. It had also come to France, the French having collected it in the vicinity of the Mississippi River in Louisiana.[11] It was glowingly described by Philip Miller in his 1731 work The Gardeners’ Dictionary.[12] One of the earliest people to cultivate it in Europe was Sir John Colliton of Exeter in Devon; scaffolding and tubs surrounded his tree, where gardeners propagated its branches by layering, the daughter plants initially selling for five guineas each (but later falling to half a guinea).[12]

Southern magnolia is a very popular ornamental tree throughout the southeastern United States and California, grown for its attractive shiny green leaves and fragrant flowers. It is also grown in Central and South America as well as parts of Asia.[4]

It is often planted in university campuses and allowed to grow into a large tree, either with dependent branches, or with the lower branches removed to display the bare trunks. It is also espaliered against walls, which improves its frost-hardiness.[4]

On the east coast of the United States, cold-hardy cultivars have been seen planted up to and even north of the Ohio River, where large tree specimens become increasingly rare and eventually are only found as shrubs before disappearing altogether from the landscape; for example, large mature trees are common in the Cincinnati, Ohio area but begin to taper off in size and occurrence until they are generally absent altogether in Columbus, Ohio. This “subtropical indicator” tree is seen in some gardens as far north as southern Connecticut, southeastern New York and Cape Cod; farther north in New England it is extremely difficult to cultivate. Towards the northern limit of its cultivation, it may suffer dieback from very hard freezes, but weathers normal freezes well.

On the west coast it can be grown as far north as British Columbia.[4]

It is recommended for seashore plantings in areas that are windy but have little salt spray.[13] The foliage will bronze, blotch, and burn in severe winters at the northern limits of cultivation, especially when grown in full winter sun[14] but most leaves remain until they are replaced by new foliage in the spring. In climates where the ground freezes, winter sun appears to do more damage than the cold itself. In the northern hemisphere the south side of the tree will experience more leaf damage than the north side of the tree. Two extremes are known, with leaves white underneath and with leaves brown underneath. The brown varieties are claimed to be more cold-hardy than the white varieties, but this does not appear to be proven as yet. Once established plants are drought tolerant, and the most drought tolerant of all the Magnolia species.[14]

The leaves are heavy and tend to fall year round from the interior of the crown and form a dense cover on top of the soil surface,[14] they have been used in decorative floral arrangements.[15] The leaves have a waxy coating that makes them resistant to damage from salt and air pollution.[14]

In the United States, Southern magnolia along with sweetbay (Magnolia virginiana) and cucumbertree (Magnolia acuminata), is commercially harvested. Lumber from all three species is simply called magnolia, which is used in the construction of furniture, boxes, pallets, venetian blinds, sashes, doors and used as veneers. Southern magnolia has yellowish-white sapwood and light to dark brown heartwood that is tinted yellow or green. The usually straight grained wood has uniform texture with closely spaced rings. The wood is ranked moderate in heaviness, hardness and stiffness; moderately low in shrinkage, bending and compression strength; it is ranked moderately high in shock resistance.[16] Its use in the southeastern United States has been supplanted by the availability of harder woods.[17]

Symbolic of the American South, Magnolia grandiflora is the state tree of Mississippi,[18] and the state flower of Mississippi and Louisiana.[6] The flower was also used as an emblem of the Confederate army in the US civil war.[4]

Cultivars

Over a hundred cultivars have been developed and named in Europe and North America. More and more plants in nurseries are propagated by cuttings, resulting in more consistent form in the various varieties available.[19] Many older cultivars have been superseded by newer ones and are no longer available.[20]

As newer cultivars have been found to be more cold hardy, the cultivated range has continued to spread farther north with some being planted around Chicago. ‘Bracken’s Brown Beauty’, ‘Edith Bogue’ and ’24 Below’ are some of the most cold hardy varieties.

  • Magnolia “Angustifolia”, developed in France in 1825, has narrow spear-shaped leaves 20 cm (8 in) long by 11 cm (4.4 in) wide, as its name suggests.[19]
  • Magnolia “Exmouth” was developed in the early 18th century by John Colliton in Devon. It is notable for its huge flowers with up to 20 tepals, and vigorous growth. Erect in habit, it is often planted against walls. The leaves are green above and brownish underneath.[21] The flowers are very fragrant and the leaves are narrow and leathery.[22]
  • Magnolia “Goliath”, was developed by Caledonia Nurseries of Guernsey, and has a bushier habit and globular flowers of up to 30 cm (12 in) diameter. Long-flowering, it has oval leaves which lack the brownish hair underneath.[21]
  • Magnolia “Little Gem”, a dwarf cultivar, is grown in warmer climates. Originally developed in 1952 by Steed’s Nursery in Candor, North Carolina, it is a slower growing form with a columnar shape which reaches around 4.25 m (14 ft) high and 1.2 m (4 ft) wide. Flowering heavily over an extended period in warmer climate, it bears medium-size cup-shaped flowers, and has elliptic leaves 12.5 cm (5 in) long by 5 cm (2 in) wide.[21]

Other commonly grow cultivars include:

  • Magnolia “Ferruginea”, has dark green leaves with rust-brown undersides.[22]
Written on June 8th, 2012 , Forestry Tags:

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