Plant 253

Magnolia grandiflora L. (Magnoliaceae)

Southern magnolia

Magnolia grandiflora is an evergreen, broadleaved tree. It is native to the south east of the United States of America, being most prevalent in Louisiana, Mississippi and Texas. It commonly reaches around 12 metres in height, although specimens have been known to grow to more than 30 metres tall. It has impressive, large leaves that are dark glossy green above with an orangey, woolly underside.

The tree's scientific name, given by Carolus Linnaeus in 1759, refers to the large, white, scented flowers which appear in cultivation in late summer and autumn. The flowers give way to infructescences which, when mature, push out red seeds that hang by threads, ready to be consumed and dispersed by birds. It is found in habitats alongside Liquidamber styraciflua, Quercus nigra and Nyssa sylvatica.

The tree and its flower have come to representative the southern American States. In 1952, Magnolia grandiflora was designated as the Mississippi State Flower, the State itself is nicknamed the Magnolia State. The champion individual of this species grows in the State and is around 40 metres tall.

Magnolia grandiflora descends from the earliest flowering plants and have flowers that are pollinated mainly by beetles. The flowers do not produce nectar; the beetles' reward is primarily pollen.

Magnolia grandiflora is a very popular ornamental and began to be favoured over Magnolia virginiana, an eastern North American species, after it was introduced to Britain. The prolific eighteenth-century collector of North America trees Mark Catesby introduced southern magnolia in 1726. It has remained in demand and there are many different cultivars available, one of the earliest ones named was Magnolia grandiflora 'Exmouth'.

On the IUCN Red List, southern magnolia is categorised as Least Concern, although potentially it has naturally occurring threats within its native habitat such as forest fires. Fire mainly affects young trees; large, old trees have adaptations to tolerate fire. The human practice of controlling naturally occurring forest fires appears to have allowed the species to extend its natural range.

Magnolia grandiflora was historically used by Native Americans in traditional medicine and continues to be studied for this purpose. Some of the reported uses and benefits include reducing high blood pressure, reducing convulsive seizures in epileptic patients and as a potential cancer treatment.

An impressive specimen, reported as 'aged' in 1912, can be seen against the North Wall at the Oxford Botanic Garden between the Herbarium Room and the Danby Arch.

Further reading

Allain LK et al. 1999. The reproductive biology of Magnolia grandiflora. Rhodora 101: 143-162.

Gottsberger G et al. 2012. Pollination ecology of Magnolia ovata may explain the overall large flower size of the genus. Flora 207: 107-118.

Outcalt KW 1990. Magnolia grandiflora L. In Burns RM and Honkals BH (eds) Silvics of North America Volume 2, Hardwoods. USDA Forest Service, pp. 445-448.

Luke Rowland