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 spheres. The pollination of flowers and dispersal of seeds are truly remarkable events because they require a long-tongued nocturnal moth and a large African antelope. This fascinating shrub belongs to the madder family (Rubiaceae) along with some economically important species, including madder & coffee.

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.

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.

Nature has provided a very special method for dispersal of the seeds of Gardenia thunbergia. 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 in the eastern Cape Region to the tropics of central Africa.

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.

In its native habitat, the blossoms of G. thunbergia are visited by nocturnal hawkmoths (family Sphingidae), similar to our 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. 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. When the moth is not feeding it can roll up its proboscis into a neat, compact coil. 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 Africantrees.com, 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.

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.

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.

The Kew Plants of the World Online (Accessed Nov. 2021) lists 137 accepted species of Gardenia; however, there are other on-line estimates as high as 200 species. One of the most beautiful is Gardenia taitensis native to islands of the South Pacific. In fact, it is the national flower of the Cook Islands and French Polynesia, including Tahiti.

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.

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.

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