Gardenias are members of the madder, or Rubiaceae, family. Though not native to either North or South America, they were named for an eighteenth-century American physician and naturalist, Alexander Garden. Gardenias were originally found only in China and Japan, but today there are over 200 different species of gardenia, mostly hybrid, in existence throughout the world. Gardenias are most prevalent in China, Japan, tropical regions of Southeast Asia and the Pacific islands, and South Africa. With proper conditions, gardenias grow into shrub-like bushes or small trees that can reach 5 ft (1.5 m) in height.
Most species of gardenia, however, are very tender plants that require an average temperature of at least 60°F (28.9°C), sunlight with some protection, and just the right amount of humidity. They often survive far better in greenhouses than outside. Gardenias are often rambling plants that form mounds of glossy dark green foliage. The leaves are oval in shape and very shiny. The flowers vary in color from pale yellow with purple markings to creamy white, and they have a classic, heavy, sweet scent reminiscent of green apple. All gardenia blossoms have an almost wax-like appearance and can be either single or double, depending on the species. Most gardenias flower in the winter or early spring, and the blossom is followed by the appearance of a large, yellowish-red, bitter-tasting berry that contains a crystalline compound called acrocetin.
The most commonly listed botanical species of gardenia include:
- Gardenia jasminoides. This species is easily the most common of these rare, fragile plants. It reaches heights of 2 ft (61 cm) and grows into a tall bushy green shrub that produces white, highly fragrant flowers. G. jasminoides is a native of China, and the gardenia most commonly used in Chinese herbal medicine. Its name comes from the fact that it was first introduced to the Western world from Cape Colony in Africa, and the aroma of its large white flowers was said to be very like the scent of jasmine.
- Gardenia jasminoides fortunata. This plant is a hybrid version of G. jasminoides that is somewhat more hardy.
- Gardenia nitida. This gardenia is a slightly taller plant that grows up to 3 ft (93 cm) and also produces white blossoms.
- Gardenia radicans floreplena. This plant is a low spreading dwarf variety from Japan that grows only to heights of 18 in (46 cm), and has double-blossomed flowers.
- Gardenia thunbergia. This gardenia grows to 4 ft (1.2 m) and is often cultivated in American greenhouses. It is found as both tree and shrub, and has white flowers with long tube-like necks.
- Gardenia rothmania. This plant is also a particular favorite of American botanists, but does not survive well in North America outside of a greenhouse. It also exists as both tree and shrub, and has pale yellow flowers with short, tube-like necks and purple markings.
Gardenias are widely used as exotic ornamental flowers in corsages, as houseplants, and in some regions, as outdoor plants. A yellow silk dye has been made for centuries from the chemical compound acrocetin extracted from the gardenia berry.
Chinese herbal medicine, however, makes the most extensive use of the gardenia. Its Chinese name is zhi zi. The traditional medicinal actions attributed to gardenia
- Gardenia gummifera. This species can be helpful in treating digestive problems, including dyspepsia and diarrhea; or used as an astringent and expectorant for nervous conditions and spasms.
- Gardenia storckii. This variety can be used in treating constipation.
- Gardenia lucida. This gardenia has antiseptic properties that can kill both bacteria and insects.
- Gardenia pseudopsidium. This species has been used to treat smallpox.
- Gardenia jasminoides. This gardenia has been found to be helpful in the treatment of pain, nose bleeds, fever, and influenza; in healing wounds and reducing swelling; and in treating mastitis, hepatitis and the hematuria that accompanies bladder infection.
- Gardenia augusta. This variety has shown effectiveness in the treatment of headaches, fever, delirium, mastitis, and jaundice related to liver problems.
- Gardenia campanulata. This plant is used in healing wounds, burns, and scalds; in reducing swelling; as a treatment for fever and influenza; in treating jaundice associated with liver problems; and in stopping bleeding.
- Gardenia labifolia. This gardenia has been found effective in treating the bites of certain snakes.
The kernel within the gardenia berry is often removed for use in herbal poultices put on sports injuries such as sprains, pulled muscles, or inflammation of nerves. The use of gardenia poultices is particularly common in Chinese medicine. Traditional Chinese practitioners make a paste of the herb with flour and wine. The powdered berry is given in both decoctions and capsules. When gardenia is used to stop bleeding it is usually burned before it is simmered in water.
Chinese herbalists state that gardenia should not be used when there is cold deficiency (watery) diarrhea present.
It is important to remember that Chinese herbal medicine is based upon individual prescriptions developed for each patient and their unique symptoms. Chinese herbs should not be taken, either individually or in formulas, unless a practitioner of Chinese herbal medicine is first consulted.
Gardenia has laxative properties, and can cause loose stools when taken frequently or in large amounts.
Molony, David, and Ming Ming Pan Molony. The American Association of Oriental Medicine's Complete Guide to Chinese Herbal Medicine. New York: Berkley Publishing, 1999.
Phillips, Ellen, and C. Colston Burrell. Rodale's Illustrated Encyclopedia of Perennials. Emmaus, PA: Rodale Press, Inc., 1993.
Reid, Daniel P. Chinese Herbal Medicine. Boston: Shambhala, 1993.
Dr. Duke's Phytochemical and Ethnobotanical Databases. http://www.ars-grm.gov/cgibm/duke/ethnobot.htm