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Ginkgo

Ginkgo biloba is a woody tree with a spreading form and a large trunk that reaches a height between fifty to eighty feet. The trees are sexually dimorphic (two-forms), and male trees typically have steep branching angles while female trees are broadly branched. Ginkgo grows in temperate climates and is long-lived, with trees up to one thousand years old having been reported.

Ginkgo is characterized by flattened, often bilobed leaves, with numerous fine veins that lack a midvein. Leaves are clustered on slow-growing, short shoots or spaced spirally on elongated shoots. Ginkgo trees are deciduous and the silhouettes of its bare branches make it easy to identify male and female trees. The pollen of Ginkgo is called prepollen because it produces a haustorial tube upon germination and only after several months releases a motile sperm cell that swims to fertilize the egg. Ginkgo is one of the most advanced land plants still fertilized by motile sperm cells. Ginkgo is a gymnosperm that produces specially modified plumlike seeds that, even though they look like fruits, botanically are seeds. The seed is surrounded by a thin papery inner seed coat, a middle shell-like hard seed coat, and a fleshy outer seed coat that ripens to a soft, pulpy, foul-smelling mass when the seeds are dropped from the female trees.

Ginkgo biloba has a long history, with ancestors extending back some 280 million years into the Permian. It is one of very few plants living today that has such a clear lineage dating back into the Paleozoic era. During the Mesozoic era the Ginkgo lineage diversified and spread to many parts of the world. During the Cretaceous, there were seven to ten species of Ginkgo trees living, and they would have been a common sight among the dinosaurs of the Northern Hemisphere. Fossil Ginkgo leaves and petrified trunks can be found during the Tertiary period in North America, Europe, and Asia where trees lived until less than five million years ago.

There is now only one living species in the family Ginkgoaceae, a once diverse and widespread group, and it is indigenous to only a small area in China. Although nearly extinct in the wild, it has been preserved as a living fossil because it was planted at the entrances to Chinese and Japanese temples. Ginkgo has commonly been planted as a street tree in temperate North American cities (such as Washington, D.C.). Male trees are often vegetatively propagated for this purpose because they lack the foul-smelling, fleshy fruitlike seeds. Ginkgo trees are quite tolerant of city pollution.

The cleaned seeds and leaves are reported to have beneficial health effects on the brain, hearing, eyes, lungs, kidneys, liver, and general circulation. The seeds are eaten and the leaves used to prepare tea. It is used for its antibacterial effects and benefits for nerves, asthma, vision, improving blood flow, and slowing aging. Several secondary metabolites such as flavonoids, terpenoids (e.g., ginkgolides A, B, and C, bilobalide, ginkgetin, and isoginkgetin), and organic acids are some of the chemicals isolated from Ginkgo. Extracts of Ginkgo are sold as a health diet supplement.