Also known as the maidenhair tree, ginkgo biloba is one of Earth's few "living fossils," being the only species in its own genus and class. Fossil evidence indicates several species of ginkgo grew widely around the world as long ago as the Permian period, 270 million years ago. The tree's range declined with the demise of the dinosaurs and was thought to be extinct until the 1600s, when it was discovered by Western travelers in Japan.
A Living Fossil
Though the total number of ginkgo species that once existed is a matter of debate among paleontologists and paleobotanists, as many as 19 distinct ginkgo tree species appear in fossil records around the world, including what is now North America and South America. The tree disappeared from American fossil records 7 million years ago and in Europe 2.5 million years ago. Fossilized leaves and parts of the ginkgo biloba tree are identical to characteristics of today's specimens, giving rise to the term "living fossil."
Paleobotanists who study ginkgo theorize that one reason the tree was so widespread in ancient times was that its seeds were easily and readily dispersed by the dinosaur species which ate the fruits. Upon the dinosaurs' demise, the ginkgo also declined, its range gradually shrinking until it was essentially confined to only a very small area in south-central China. Today, squirrels are the main dispersers of ginkgo seeds, though ginkgo has naturalized into forests on its own in some parts of Korea where the tree is planted as an ornamental.
Saved by Monks
Chinese monks commonly grew rare and precious plants within the confines of the monastery walls. Ginkgo is thought to have been cultivated in these Buddhist monasteries from as early as 1100 A.D., though how widespread the tree was before this date is unknown. Ginkgo is known to be an exceptionally long-lived species, with some trees in China reputed to be 4,000 years old. Partly because no surviving native stands of ginkgo trees have been confirmed by science, the species is believed to have survived into modern times largely because of this human assistance.
Brought to the West
Monks brought the ginkgo to Japan in the early 12th century, where it was grown on temple grounds and in monasteries. While on a mission to Japan for the Dutch East-India Company in 1691, German botanist and physician Engelbert Kaempfer first saw a living ginkgo tree while visiting Nagasaki. Unknown in Europe prior to his return in 1692, Kaempfer brought seeds of the tree back to Holland, and one of the trees he planted in the Utrecht Botanical Garden still lives as of 2010. Ginkgo then spread to other parts of Europe, finally arriving in America in 1784 via the garden of James Hamilton, who lived outside Philadelphia.
Modern Day Usage
Soon after its introduction in the 1800s to North America, ginkgo spread rapidly as an urban ornamental tree--even then the species was known to be particularly hardy and resistant to ailments that commonly affect other tree species. It is still used as an urban street tree, primarily because of its tolerance of pollution, resistance to attacks by insects and disease. In its youth, the tree grows very straight and rather rapidly, adding a foot of new growth each year in the first 30 years of life. Mature specimens have angled, somewhat narrow canopies.
Ginkgo and the A-Bomb
Ginkgo's reputation as an exceptionally tough tree was bolstered after Western forces dropped atom bombs over Hiroshima on Aug. 6, 1945 and Nagasaki on Aug. 9, 1945. Half a dozen mature ginkgo trees within several hundred to 2,000 meters of the blast center in each city not only withstood the blast relatively intact, but also revived and continued to grow without evidence of deformity in the decades following the bombing. In some cases, adjacent structures that were obliterated helped shield the trees from the blast. In virtually every instance where surviving trees were found, buildings were re-constructed around trees out of reverence for the tree and its historical significance.