Gardenia thunbergia - Jan Feb 2020 Plant of the Month
An unusual Gardenia: The mission of the Growing Friends is to propagate unusual and beautiful plants from the Royal Botanic Gardens and to make them available to the public by the Growing Friends at its autumn and spring sales each year.
Gardenia thunbergia is one such beautiful shrub, with showy, heavily perfumed flowers and decorative fruits. It is evergreen, two or more metres in height with a smooth, usually straight, whitish-gray main stem and short branchlets. The glossy deep green leaves are carried in whorls near the end of the branchlets. The flowers are large showy, creamy white and heavily perfumed particularly at night. They open from elegantly furled creamy-green buds and do not turn yellow as they age on the bush. Flowers are produced abundantly generally in late summer.
Gardenia thunbergia occurs naturally on the eastern coast of South Africa, primarily in evergreen forest and forest margin. Its fruit are hard and woody, they do not burst split, or drop and can remain on the shrub for years. They are adapted to being eaten by elephants, large antelope and buffalo, and the seeds are tough enough to pass through their digestive systems unscathed. The seeds are not released from the fruit unless these animals eat them. Natural seed dispersal is, therefore, most unlikely in Australia
Naming and history: The botanical name for the genus Gardenia was in honour of Dr Alexander Garden who was born in Scotland in 1730, and practised in South Carolina, USA. He corresponded with Carl Linnaeus. The species, thunbergia, was named after Carl Thunberg, a pupil of Linnaeus.
In Afrikaans the common name is buffelsbal which means buffalo testicles, a reference to the shape of the fruit. The Zulu name umvalasangweni means the back-gate closer as it is used as gates for cattle kraals. The wood is heavy, dense and extraordinarily hard and has the ability to bend without breaking but its uses are limited because the branches are small. The roots are widely used in Africa as a folk medicine particularly for skin diseases and lesions.
Gardenias are grown mainly for their flowers but it is intriguing to note that they are part of the very large Rubiaceae family. Another member of this family is the South American tree, Cinchona, and quinine extracted from bark of the Cinchona tree was the first drug used to treat malaria. Coffee, Coffea arabica, is also a member of family Rubiaceae.
Cultivation notes: Gardenia thunbergia is easy to grow, although slow growing and frost tender. It does best in sun or semi-shade in slightly acid, well-drained soil with plenty of organic matter. Although it is moderately drought tolerant it should be mulched thickly and regularly and benefits from regular deep watering. Yellowing leaves can usually be corrected by feeding with a fertiliser that includes trace elements.
It is a handsome shrub that may be used as a specimen plant on a lawn, or as part of an informal hedge or shrubbery. This article uses information provided by Alice Notten, of the Kirstenbosch National Botanical Gardens. www.plantzafrica.com
There are fifteen specimens of Gardenia thunbergia in the Royal Botanic Gardens, Melbourne, two are in the Southern African Collection, reference 20 on the Gardens Guide map available at entrances to the Gardens.
The Growing Friends Nursery (which is open to the public most Friday mornings) has a supply of this plant for sale.
Thanks to Bronwen Hamilton for supplying this article.