Trinity's trees - featuring the Southern Magnolia

Posted on: 28 September 2023

M. grandiflora is a broadleaved evergreen tree, native to the south-eastern United States where it grows in moist wooded areas from North Carolina to Florida. It was introduced to Europe by French botanist Pierre Magnol over 300 years ago and was named in his honour. It can grow in a variety of locations, if mild and sheltered {1} and can often be found growing up against the side walls of buildings where they are protected. They have quite long, tough, oblong, leathery leaves with a thick coating of downy orange hairs on the underside. One of the main features of this tree is its spectacular white flowers which bloom through summer into autumn. They are large and cup-shaped, opening to 25 cm to 30 cm in diameter, and are highly fragrant with a sweet lemony citronella scent. The flowers possess both male and female reproductive parts and are known as perfect flowers.

Magnolia grandiflora is an ancient angiosperm (a flowering plant with its seed enclosed in a fruit) tree in the family Magnoliaceae. Magnolias are among the oldest living flowering plants and are present in the fossil record from the Creataceous period, around 95 mya {2}. This was before the existence of the common pollinating insects we generally think of, such as bees. Thus, magnolias evolved to be pollinated primarily by the flightless beetles that fed on the flowers’ pollen. These beetles were often considered ‘dumb pollinators’ as they unwittingly spread pollen to the flowers’ anthers while feeding [3}. Beetles have strong mouthparts (mandibles) designed for chewing not pollinating, so the magnolia carpel (female parts) is very tough to withstand the feeding beetle. Today the flowers are pollinated by bees and other pollinating insects.

Magnolia grandiflora possesses some of the most primitively structured fruit amongst angiosperms,  generally classed as a follicetum which is an aggregate fruit composed of many fused carpels containing the seeds which are bright red in colour. {1} The fruits are large and cone shaped and add to the ornamental appeal of the tree. The seeds, while functioning primarily for reproductive purposes, also provide a food source for numerous animals.

This Southern Magnolia is tree number 433 and you can also find a mature flowering specimen in the Walled Garden at Trinity College Botanic Garden.  

Thanks to Michelle Murray, John Parnell and Stephen Waldren for providing this information and caring for Trinity’s beautiful trees. 

1            https://naturewalk.yale.edu/trees/magnoliaceae/magnolia-grandiflora/southern-magnolia-58

2            https://www.britannica.com/plant/Magnoliid-clade#ref72769

3            https://extension.illinois.edu/blogs/garden-scoop/2018-05-05-magnolia-pollination

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