The ginkgo, or maidenhair tree (Ginkgo biloba) is an unusual species of gymnosperm, having broad leaves, and seasonally deciduous foliage that turns yellow and is dropped in autumn. The ginkgo is a dioecious plant, which means that male and female functions are performed by separate trees. The ginkgo is famous as a socalled "living fossil," because it is the only surviving member of the family Ginkgoaceae and the class Gingkoales. This is a group of gymnosperms with a fossil lineage extending back to the lower Jurassic, some 190 million years ago, and once probably having a global distribution.
In more modern times, the natural distribution of the ginkgo was apparently restricted to a small area of southeastern China. It is very likely, however, that there are no longer any truly natural, wild populations of ginkgo in forests in that region. It appears that the only reason this remarkable species still survives is because it was preserved and cultivated in small groves around a few Buddhist temples. This was apparently done because farsighted monks recognized the ginkgo as a special, unique species of tree, and because they valued its edible, possibly medicinally useful fruits and leaves. Gingko is still being used in this way today, as a "herbal" or "folk" medicine thought to be useful in the treatment of memory loss, asthma, circulatory disorders, headaches, impotence, and a variety of other ailments.
Today, the ginkgo is no longer a rare species, and it has a virtually worldwide distribution in temperate climates. This is because the ginkgo has become commonly grown in cities and gardens as a graceful and interesting shade tree. The ginkgo has attractive, golden-yellow foliage in autumn, is easy to transplant and cultivate, and is remarkably resistant to diseases, insects, and many of the stresses of urban environments including, to some degree, air pollution. The ginkgo is also often cultivated because of its special interest to botanists and others as a living fossil.
Often, an attempt is made by horticulturists to only plant male ginkgos, because the outer flesh of the fruits
of female trees can have an uncomfortably foul odor, making some people nauseous, and causing skin rashes upon contact. Ginkgo trees can reach an height of about 115 ft (35 m), and can achieve a trunk diameter of more than 27 in (68.5 cm). Trees mature at about 20 years, and can live to be older than 1,000 years.