|Ginkgo biloba L.|
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). The Ginkgopsida is now usually placed in the division Ginkgophyta. In the past it has also been placed in the divisions Spermatophyta or Pinophyta.
Its name means "silvery apricot" (銀杏 yin2 xin4) in Chinese. The same name is used in Japan, where ginkgo later transplanted, 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 are the same).
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. The common name "maidenhair tree" is because the leaves resemble some of the pinnae of maidenhair ferns. 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 "fruiting spurs", where they are clustered at the tips.
The seed is small, and inside a light yellow-brown coloured, fruit-like coating. It is plum-like and attractive, but it contains butyric acid and thus smells like rotten butter. The seed is similar in appearance to a pistachio, and edible when cooked. The nuts are a traditional Chinese food, and sometimes believed to have health benefits. The trees are easy to propagate from seed.
The sexes are separate, some trees being female and others being male. 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 considered a living fossil, with recognizable specimens of related ginkgos dating back 270 million years. It has long been cultivated in China. 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 Confucianism the ginkgo is also widely found 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. This makes it all the more puzzling why all of its relatives died out. For this reason, and for their general beauty, they are a favorite among urban shade trees.
Ginkgos are often very long-lived. Some specimens are thought to be more than 3,500 years old.
Extracts from the ginkgo leaves contain flavonoid glycosides - among others - ginkgolides and are therefore used as a pharmaceutical. The extract has many properties but it mainly used as memory enhancers and anti-vertigo agents. However, recent studies have called into question its efficacy.