Ginkgo
The
Ginkgo (
Ginkgo biloba), sometimes also known as the
Maidenhair tree, is a unique
tree in the world today. It has no known close relatives, existing within its own class, the
Ginkgoopsida (order
Ginkgoales, family
Ginkgoaceae, genus
Ginkgo), one of the best examples of a
living fossil. The Ginkgoopsida is now usually placed in the division
Ginkgophyta. In the past it has also been placed in the divisions
Spermatophyta or
Pinophyta. Ginkgo is a
gymnosperm (as opposed to an
angiosperm), meaning "naked seed"; its seed embryos are not protected by a seed shell at pollination, but are exposed to the air.
Its name means "silver
apricot" (銀杏 yín xìng) in
Chinese. The same name is used in
Japan, where Ginkgo came later than in China through seeds, but the Japanese pronunciation is ginkyō, and this is what the Westerners heard in the eighteenth century. However, the modern Japanese reading is ichō or ginnan (although the
Kanji text is the same). The modern Chinese name for it is 白果 (bái guǒ), meaning "white fruit."
The leaves are also unique among seed-bearing plants, being fan-shaped with veins radiating out with the leaf blade, sometimes bifurcating but never anastomosing (branching). The old popular name "Maidenhair tree" is because the leaves resemble some of the pinnae of the
Maidenhair fern Adiantum capillus-veneris. Sometimes leaves are notched or lobed, but only from the outer surface, between the veins. The leaves are borne both on the more rapidly-growing branch tips, where they are alternate and spaced out, and also on short, stubby spur shoots, where they are clustered at the tips.
The seed is a 1.5-2cm
nut, contained inside a light yellow-brown coloured, soft fruit-like coating 2-3cm in diameter. It is plum-like and attractive, but contains
butanoic acid and thus smells like rancid
butter (which contains the same chemical). Some people are sensitive to this or other chemicals in the fruit pulp, and when cleaning the nuts they should be handled with care, wearing disposable gloves, if sensitive. The symptoms are a rash or
blisters similar that from
poison-ivy. The seed is edible after shelling and after being cooked. Japanese cooks add it to dishes such as chawammushi. The nuts are a traditional Chinese food, often served at weddings, and sometimes believed to have health benefits; some also consider them to have
aphrodisiac qualities (unproven!). The trees are easy to propagate from seed.
The sexes are separate, some trees being female and others being male. In some areas, most trees planted are male stock grafted onto roots propagated from seed, because the male trees will not produce the smelly fruit.
The Ginkgo is a
living fossil, with recognizable specimens of related ginkgos dating back 270 million years. It has long been cultivated in
China; some planted trees at temples are believed to be over 1,500 years old. The first record of Europeans coming across it is in
1691 in Japanese temple gardens. Even so, for centuries it was thought to be extinct in the wild, but is now known to grow in at least two small areas in western China. Because of its status in
Buddhism and
Confucianism, the Ginkgo is also widely planted in Korea and parts of Japan.
The Ginkgo has the intriguing distinction of being one of the world's most urban-tolerant trees, often growing where other trees cannot survive. Some claim that only one tree, the
Tree-of-heaven, is more urban-tolerant. This makes it all the more puzzling why all of its relatives died out. For this reason, and for their general beauty, they are excellent urban trees.
Ginkgos are often very long-lived. Some specimens are thought to be more than 2,500 years old.
\nGinkgos are sometimes grown as penjing, a Chinese art similar to
bonsai; they are kept artificially small and tended over centuries.
The oldest Ginkgo fossils are from the
Permian. In earlier times the Ginkgos wasn't so alone. In the
Cretaceous, there was in their primetime at least five species existing after they had spread and diversified throughout
Laurasia during the middle
Jurassic.
In the
Paleocene,
Ginkgo adiantoides was the only Ginkgo species left, at the end of the
Pliocene Ginkgo adiantoides disappeared from fossil record and western botanists thought that all Ginko species were extinct until the German physician and botanist
Engelbert Kaempfer in 1691 found
Ginkgo biloba trees that buddhist monks had cultivated, when travelling to Japan for the Dutch East-Indies Company.
Traditionally many fossils have been classified in the genera
Ginkgo,
Baiera and
Sphenobaiera.
Ginkgo has been used for classifying plants with leaves that have more than four veins per segment, while
Baiera for those with less than four veins per segment.
Sphenobaiera has been used to classify plants with a broadly wedge-shaped leaf that lacks a distinct leaf stem. Recently many scientists belive that these are all just variations of the Ginkgo genus.
Medical uses
\nExtracts from the Ginkgo leaves contain flavonoid glycosides - among others - ginkgolides and are therefore used as a pharmaceutical. The extract has many properties but it is mainly used as memory enhancer and anti-vertigo agents. However, studies differ about its efficacy.
Benefits
\nThroughout the past three decades, more than 300 studies have shown Ginkgo biloba to provide a number of benefits. The most important are listed below.
- Increases blood flow to the brain and throughout the body's blood vessels that provide blood and oxygen to the organ systems\n*Increases metabolism efficiency, regulates neurotransmitters, and oxygen levels in the brain\n*Enhanced circulation in the brain include improved short and long term memory, reaction time and mental clarity\n*Helps control the transformation of cholesterol to plaque associated with the hardening of arteries, and may relax constricted blood vessels\n*Ginkgo has been shown to be a supportive herb for treating infertility in males or impotence\n*Aids in preventing damage to organs from free radicals, and also blocks the platelet activating factor which causes some skin disorders such as psoriasis\n*Helps in the treatment of eye and ear disorders
Side effects
\nLike all things, Ginkgo may have some undesirable effects, especially for individuals with blood circulation disorders and those taking anti-coagulants such as aspirin. It should also not be used by people who are taking the anti-depressant drugs known as monoamine oxidase inhibitors (MAOI) or pregnant women.
Below are some Ginkgo side effects and cautions:
- gastrointestinal discomfort\n*headaches\n*may increase risk of bleeding, and should not be used if you have a clotting disorder\n*Ginkgo should not be used by pregnant women\n*restlessness\n*diarrhea\n*nausea\n*vomiting
If any side effects are experienced the dosage should be lowered immediately. Ginkgo supplements are usually taken in the range of 40 mg to 200 mg per day. If the side effects continue usage should be stopped completely.
External links
\n* The Ginkgo Pages: all aspects, in English, German, French, Spanish and Dutch\n*
University of California Museum of Paleontology\n*
Gymnosperm Database\n*
The Ginkgo Museum, Weimar/Germany
