Peter Crane

Imagine a tree so beautiful Goethe wrote a poem about it. Imagine one so ancient it coexisted with the dinosaurs. Imagine one so hardy it could survive 0.5 miles from the epicentre of the bomb in Hiroshima. All these things are true of Ginkgo biloba.

The cut fan shape of its leaves is instantly recognizable, as is its yellow fall colour. It is found on city boulevards, university campuses, in botanical gardens, beside Asian temples, and gracing home gardens, yet today it is practically non-existent in the wild. How did it go from naturally plentiful in the Pleistocene era to a cultivated plant today?

Fossil records show that ginkgos had a range from Tasmania to Iceland and Greenland 40 - 65 million years ago. As the global climate cooled and dried, they seem to have disappeared from the southern hemisphere some 35 million years ago, from North America about 15.5 million years ago, and from Europe about 5 million years ago. They did survive in China, most likely centred in the Jinfo Mountain area of Chongqing and the Tianmu Mountain area in Zhejiang. The first mention of Chinese cultivating ginkgos is in the ninth century CE. They were reintroduced by traders to Japan and Korea about the middle of the 15th century. Western scientists and plant hunters brought what was a novel plant to them to Europe where it created a sensation in the second half of the 18th century. William Hamilton carried it to North America in 1784.

One of the theories advanced for the almost complete disappearance of ginkgos came from Bruce Tiffney in 1984, building on the work of Janzen and Martin. Tiffney suggested that the trees had lost their major dispersal agents. Like many fruit and nut trees, ginkgos rely on animals to spread their seeds. As animals moved to more attractive climates as the earth grew colder, the trees were left standing in place, unable to colonize. Caught in an extinction vortex, they almost disappeared completely.

Can a plant that basically doesn't exist in the wild survive today? Indications so far are good, especially as new cultivars are developed from naturally occurring mutations. Perhaps their greatest enemy today is humans. Ginkgos are dioecious plants, meaning there are male trees and female trees. Fertilized seeds fall to the ground, where they emit an incredibly rancid smell, perhaps the one that attracted the tree's prehistoric dispersers. Humans are repelled by this smell though, and so those who feel the natural world can always be made prettier, neater, and cleaner purchase male plants. No chance of upsetting smells there, but also no opportunity for natural spread.

Crane also speaks of a caretaker cutting down a pair of two hundred year old trees because his dog repeatedly ate the seeds and became ill. As he says:

Trees and forests that have stood firm for centuries in the face of repeated natural assaults have no power to resist one fleeting, but often devastating, attention.

[[Peter Crane]] is someone who really knows his subject. He has been director of the Royal Botanic Gardens at Kew, taught at the University of Chicago, and been Dean of the School of Forestry and Environmental Studies at Yale. His book covers just about every aspect of Ginkgo you can think of, from morphology and phytochemistry, to its use in visual arts. There is something here for everyone. It's hard to imagine a more comprehensive general study.… (más)