Gardenia Family

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Economic Plant Photographs #42

The Gardenia, The Kudu & A Long-Tongued Moth

The Story Of An African Shrub & Two Symbiotic Animals

  1. Seed Dispersal By Large African Antelopes
  2. Pollination By Nocturnal, Long-Tongued Moths
  3. Gardenia Blossoms Used For Fragrant Perfumes  
  4. Other Members Of The Madder (Coffee) Family
  5. A Few References About Gardenia thunbergia

There are many fascinating relationships between plants and animals, but one of the most unusual involves a beautiful South African shrub (Gardenia thunbergia), and two very diverse animals. Unlike most plants, the fruits never open or fall from the branches. Instead, they remain firmly attached like large, wooden eggs. The pollination of flowers and dispersal of seeds are truly remarkable events because they require a long-tongued nocturnal moth and a large antelope.

In its South African habitat of evergreen forest, woodland and bushveld, Gardenia thunbergia is a large shrub or small tree up to sixteen feet tall (5 m). The leaves are glossy light green, crowded in whorls of three or four near the ends of the branchlets. Gardenia thunbergia occurs in a strip up the eastern coast of South Africa, from near Grahamstown in Eastern Cape to Kosi Bay in the north of KwaZulu-Natal. This species was the first of the South African gardenias known to botanists, and was introduced to Kew in 1773.

Native people use the roots of G. thunbergia as a treatment for numerous ailments, including skin diseases, skin lesions caused by leprosy, and as an emetic against fever. The rootbark is used as an emetic for biliousness and to treat gall bladder problems. The roots and leaves are used in various parts of Africa to treat syphilis, and the latex is used as a purgative.

1. Seed Dispersal By Large South African Antelopes

Seeds provide the vital genetic link between successive generations of plants. The are produced and packaged in botanical structures called fruits. Fruits come in an endless variety of shapes and sizes, from papery, inflated pods of locoweeds (Astragalus) to fleshy berries of grapes (Vitis) and tomatoes (Lycopersicon). Unlike the fleshy fruit of the common cultivated garden (G. jasminoides), the fruit of G. thunbergia becomes woody with a thick outer wall (pericarp). They remain persistent on the branches like a swollen stem or gall. Each oval fruit is about three to four inches (7-10 cm) in length and may contain up to 600 hard, angular seeds.

Woody fruit of Gardenia thunbergia showing the thick wall (pericarp) and mass of hard, angular seeds. Each fruit may contain up to 600 seeds.

Nature has provided a very special method for dispersal of the seeds. Several large South African antelopes, including the greater kudu, lesser kudu and Cape buffalo chew open the woody fruits and eat the seeds. According to Rudolf Marloth (The Flora of South Africa, 1932), the hard seeds pass unharmed through the ungulate digestive system and become dispersed in the dung of these large herbivores. Some seeds may also be released when the fruits decay, or when partially decomposed by fire. Seed dispersal by browsing animals may account for the widespread distribution of Gardenia thunbergia throughout the African veld, from Algoa Bay the Cape Region to the tropics of central Africa.

The woody, unopend fruit of Gardenia thunbergia. Unlike most other plants, these woody pods never split open to release their seeds. They are typically chewed open by lage herbivores.

A kudu standing camouflaged in the bushes of Kruger National Park, South Africa. Photographed by P. Armstrong.

Dispersal Of Large Tropical Fruits By Big Animals

2. Pollination By South African Long-Tongued Moths

The striking blossom of Gardenia thunbergia is quite different from the common gardenias (G. jasminoides) cultivated in southern California gardens. It consists of a rosette of eight or nine white petals at the end of a slender flora tube five inches (12 cm) long. Nectar glands at the base of the long floral tube produce copious amounts of sweet fragrant nectar, but it is inaccessible to most insects and birds. A tough green calyx sheath at the base prevents large bees, such as carpenter bees (Xylocopa) and bumble bees (Bombus), from chewing through the delicate inner corolla tube. The opening of the corolla tube is lined by a ring of eight anthers which are heavily laden with pollen.

Left: The scented flower of Gardenia thunbergia consists of eight or nine petals at the end of a slender floral tube. Only long-tongued hawkmoths can reach the sweet nectar deep inside the floral tube. Right: Longitudinal section of a flower showing the long, slender floral tube. The entrance to the floral tube is surrounded by a ring of eight anthers that shed copious pollen.

In its native habitat, the blossoms of G. thunbergia are visited by nocturnal hawkmoths (family Sphingidae), similar to out western North American Manduca moths that pollinate jimsonweeds (Datura wrightii). They are called sphinx moths because the alarm posture of some larvae resemble the form of the Egyptian sphinx. Some hawkmoths have tongues (proboscides) up to 5.5 inches (14 cm) long (or longer), long enough to reach the plentiful supply of nectar deep within the floral tube. The proboscis roles up into a neat, compact coil when the moth is not feeding. When the proboscis is inserted into the floral tube, it passes through a ring of eight stamens which are heavily laden with pollen. Pollen adheres to the sticky proboscis and other furry body parts and is transferred to other flowers as the moths feed. Anthers of individual flowers mature and shed pollen before the stigma is receptive, a maturation sequence conducive to cross pollination. This maturation sequence is called protandry (1st + male).

A North American hawkmoth (Manduca sexta) with its four inch (10 cm) proboscis fully extended. Note the six orange spots on the moth's abdomen. A related species (M. quinquemaculata) has five orange spots.

Another African gardenia is called Transvaal or bushveld gardenia (Gardenia volkensii). This shrub or small tree may grow up to 26 feet (8 m) tall, and is native from Angola to KwaZulu-Natal. Like G. thunbergia, this species has fragrant white blossoms and woody seed pods that remain on the branches. Livestock and large game browse the leaves, and the fruits are eaten by elephants, kudu, velvet monkeys and baboons. According to, the fruits and roots are used in the treatment of a variety of ailments, including asthma, infertility, earache, sore eyes, epilepsy and headache. Ashes from burnt roots are placed on the chest as a treatment for pneumonia. Some local people also believe that this shrub will protect them from lightning.

Transvall gardenia (Gardenia volkensii). This shrub or small tree may grow up to 26 feet (8 m) tall, and is native from Angola to KwaZulu-Natal. Like G. thunbergia, this species has fragrant white blossoms and woody seed pods that remain on the branches. The fruits are distinctly ribbed, unlike the smooth fruits of G. thunbergia.

In the southwestern United States there are several species of large, night-flying hawkmoths. One of the most common is Manduca sexta, also known as the tomato hornworm. Probably every vegetable gardener has observed the large, ravenous caterpillar devouring their tomato plants. Tomato hornworm adults are frequent visitors of the large, white, trumpet-shaped blossoms of jimsonweed (Datura wrightii), a common roadside plant in the American Southwest. These large moths also visit several cultivated flowers, such as four o'clocks (Mirabilis), columbine (Aquilegia), evening primrose (Oenothera), night-blooming cereus (Cereus) and occasionally cultivated shrubs of G. thunbergia.

Left: A jimsonweed (Datura wrightii) in the fertile San Pasqual Valley of San Diego County. Right: The larva of Manduca sexta on the spiny fruit of a jimsonweed. This camouflaged larva is better known to tomato farmers as the tomato hornworm.

More Photos Of The Jimsonweed & Its Moth
More Photos Of The Jimsonweed Blossoms
See Article The About Alkaloids Of Datura

3. Fragrant Gardenias Used For Perfume

Gardenia nectar contains fragrant essential oils which serve to attract insects for pollination. Night-blooming species typically have white blossoms that attract a variety of moths. These very fragrant nectars are commonly used in the perfume industry. Essential oils are chemically very different from true oils, like unsaturated fats of seeds. They are volatile mono and sesquiterpenes, the same class of chemicals that impart the distinctive odor and flavor to many herbs and spices. Gardenia perfume is obtained by solvent extraction from flowers of several species of Gardenia, including G. jasminoides. One of the main centers for commercial extraction of fresh flowers is Reunion, an island in the Indian Ocean east of Madagascar.

4. Other Members Of The Madder Family

The genus Gardenia belongs to the mostly tropical madder family (Rubiaceae), along with several economically important trees and shrubs. The bark from several species of Cinchona native to the Andes region yields quinine, an important alkaloid used in the treatment of malaria. A brilliant scarlet dye is obtained from the roots of the madder plant (Rubia tinctorum). In fact, this was the dye used to color the uniforms of the British during the American Revolutionary War. The seeds of the coffee plant (Coffea arabica) are roasted and ground to produce one of the world's largest beverage crops. Also in the madder family is the common cultivated shrub with shiny green leaves called mirror plant (Coprosma) and a number of shrubby or climbing natives in the chaparral and forested regions of California called bedstraw (Galium). The Polynesian painkiller tree called "noni" (Morinda citrifolia) has been used native people for centuries. It is now sold commercially as a treatment and preventive therapy for many ailments.

Quinine From The Cinchona Tree
Drink From The Painkiller Tree
Coffee: A Valuable Beverage
A Red Dye Called Madder

Gardenia thunbergia is an attractive ornamental shrub for southern California gardens. It produces striking white blossoms with a very fragrant scent. In fact, local southern California hawkmoths occasionally visit its blossoms for a sweet nectar reward. Unless you happen to have an African kudu browsing in your yard, you might need a sledgehammer or saw to break open the woody seed pods.


  1. Armstrong, W.P. 1986. "The Gardenia, The Kudu, and a Long-Tongued Moth." Zoonooz 59 (1): 17-19

  2. Hutchings, A. 1966. Zulu Medicinal Plants, An Inventory. University of Natal Press, Pietermaritzburg.

  3. Marloth, R. 1932. The Flora of South Africa Volume III: Sympetalae. Wheldon & Wesley, Ltd., London.

  4. Palmer, E. and N. Pitman. 1961. Trees of South Africa. A.A. Balkema, Cape Town.

  5. Pooley, E. 1993. The Complete Field Guide To Trees of Natal, Zululand and Transkei. Natal Floral Publications.

  6. Neuwinger, H.D. 2000. African Traditional Medicine: A Dictionary of Plant Use and Applications. Medpharm GmbH Scientific Publishers, Stuttgart, Germany.

  7. Schery, R.W. 1972. Plants For Man. Prentice-Hall, Inc., Englewood Cliffs, New Jersey.

  8. Sunset Books & Sunset Magazine (Editors). 1995. Sunset Western Garden Book. Sunset Publishing Corporation, Menlo Park, CA.

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