Tree of beauty, tree of healing

kw: book reviews, nonfiction, trees, natural history

The Ginkgo is not only one of the most beautiful trees, it is distinctive. Once you have seen one, you will likely recognize one at a distance. Here in the U.S., few have seen really big ginkgo trees. The oldest one in the country is probably one in Georgia that is said to be 222 years old, planted to commemorate a visit by George Washington in 1791. The largest is probably one in Connecticut, planted in 1860, and 33m (110ft) tall. Several American ginkgoes have a girth of about 5m (16ft), or a diameter in the range of 1.6m (5ft). Compare those with one in Yongmunsa, Korea, that may be as old as 1,100 years, with a height of 62m (203ft), a girth of 14m (46ft) and thus a diameter near 4.5m (15ft). One tree in China has a diameter over 5.8m (19ft). However, most of the "street tree" ginkgoes in the West are less than 100 years old, perhaps 20m (65ft) tall and half a meter (20in) in diameter. I see a row of ginkgo trees of about that size when I visit the Hagley Museum near Wilmington, Delaware.

The Chinese, Japanese and Koreans seem to have found a medicinal use for almost everything. While the American FDA has about 800 approved drug substances (and more than 100,000 formulations), an apothecary shop in Asia is likely to have 10,000 or more ingredients and an uncounted number of ways of compounding mixtures. Extracts and other preparations of ginkgo leaves, seeds and bark are used to treat many bodily ailments. In the West, we seem to limit ourselves to a leaf extract that is mildly effective for memory problems and perhaps for some forms of dementia. My mother used it once she began to suffer dementia (my father remembered for her, when to take it).

A very comprehensive and readable account of ginkgo natural history is found in Ginkgo by Peter Crane, former Director of the Royal Botanical Gardens of Kew, England. I knew the genus Ginkgo is ancient but I didn't realize just how ancient. Though the species Ginkgo biloba as described by Linné is a few millions or tens of millions of years old, numerous fossil ginkgo species date back as far as 300 million years or more. The ginkgo line survived the great Permian mega-extinction event. However, they almost didn't survive the Pleistocene!

A few million years ago, a small number of different ginkgo species had worldwide distribution. The ice ages that began about 5.5 million years ago, and ramped up in earnest some 2.5 million, nearly did them in. By about 5,000 years ago, as well as botanists and paleontologists can determine, only a few small groves of ginkgo trees survived in remote parts of China. However, humanity, the agent of the current mega-extinction, in this case saved the ginkgo, partly because the Chinese liked the edible nuts, and perhaps also because of their beauty (I suspect if poison ivy were in danger of extinction, most people would gladly let it go!).

In seven sections and 37 compact chapters, Dr. Crane introduces us to the natural history of the tree, its ebb and flow through time, and how ginkgoes and humans have interacted for at least a couple of thousand years. Most folks are impressed by things like record size, but these are neither the largest of trees, nor the longest-lived. They have other unique features.

As I mentioned above, the tree's outline is distinctive, though certain old pine trees can look very similar. But the leaf! There is nothing like it. The species was named for its bilobed leaf. Not all ginkgo leaves have the central cleft, and on older trees, few do. But with or without it, the fan-shaped leaf is unique. It is said that the Chinese love the ginkgo because its leaves resemble their paper fans. I suspect the leaf inspired the paper fan!

Also, in contrast to all the common "hardwood" trees, the ginkgo is not a flowering plant. It is more closely related to "seed ferns". The male tree bears small pollen cones, and the female tree bears somewhat larger ovule cones. They are wind pollinated. Few trees are dioecious (that is, having separation of sexes), but some familiar trees are, such as red maple and yew. But ginkgo pollen is absolutely unique. The sperm swims to the ovum, once released from the pollen grain upon contact with the ovule. Finally, ginkgo leaves turn yellow, seemingly all on the same day, in early fall. Where they have been naturalized into a forest, an aerial view of the forest in early October (in the North, anyway!) will have a polka-dot appearance. By the time their yellow leaves fall, the reds of maples and other such trees will dominate.

Because of quirks of human nature, ginkgoes have been preserved. Without, they might have gone extinct hundreds of years ago. Can we muster up a sufficiently widespread love of other trees that are now endangered, to preserve them as effectively?