The ginkgo tree: a living fossil
By Robert A. Hedeen, Naturalist
Scattered about the streets and parks in most major cities in the United States is a non-native species of tree that represents the last vestige of a great group of plants that reached their peak of diversity during the Age of Dinosaurs some 200 million years ago. It is an Asian species but is known from fossils from Alaska to Europe and was thought to be extinct in the wild before living specimens were found. It is the ginkgo tree and was called a living fossil by Charles Darwin, and its survival through the eons of time fascinated the great naturalist.
Numerous thriving ginkgo trees are to be found the in Rock River Valley, with some areas of Rockford having several of them lining streets (Robey Street, just south of North Towne Mall). Of course, they are not native species but have been planted for landscaping effects.
Once there were many species of ginkgoes covering the temperate and tropical regions of the world, but, as climatic and geological changes occurred, most of them perished or evolved into new species better adapted to the environment. The same thing happened with many other plants and animals inhabiting the earth at that time.
Today only one species, Ginkgo biloba, remains. Ecologists call the ginkgo tree a relict species, a holdover from the distant past. As it is an aesthetically desirable tree, this native of Asia has been planted extensively along streets and in parks in many cities of the United States and abroad. Years ago, horticultural experts in Washington, D. C. planted a large number of them in the capital and several famous streets and avenues are lined with ginkgoes.
The ginkgo is easily recognized by its fan-shaped leaves, and, when the leaves have been dropped in the fall, by the short twigs that look something like miniature stumps along the bare branches. To some, the leaves resemble the fronds of the maidenhair fern, and the tree is frequently called the maidenhair tree. The leaves turn a beautiful yellow in the fall.
The ginkgo tree is considered to be a sacred plant by Buddhists, and for hundreds of years it has been cultivated in China, Japan, and Koreaespecially on the grounds of temples. It was formerly believed this careful nurturing of the tree is what saved it from extinction. A few decades ago, however, considerable numbers of them were found growing in the wild in two remote provinces of eastern China.
European adventurers to Asia brought the tree home in the 17th century, and it was eventually exported to the U.S. and other parts of the world. It is a hardy species and will thrive in a wide range of climates and soil types. It is amazingly resistant to disease organisms and damaging insects, and it can tolerate the polluted air of cities that kills native trees.
The ginkgo is a unisexual (dioecious) plant, and the male tree is the one preferred for landscaping. The female tree produces an abundance of plum-like fruits that litter the ground. When crushed, the fruit emits a foul odor that is usually described in other than polite language. I do not think the odor of the fruit is as nauseating as some describe it. It smells like rancid butter to me.
When the soft, fleshy, outer covering of the fruit is removed, a 1/2-inch white pit is revealed (the name ginkgo is Chinese for silver-white nut). In the Orient, the smooth, silvery pit, which lacks the offensive odor, is considered a delicacy. The nuts are toasted in a manner similar to how we roast chestnuts and almonds.
Though there is only one species of ginkgo tree living in the world today, botanists have developed different varieties of the plant. The fastigiata type is columnar in shape with semi-erect branches, the pendula variety has drooping branches, and the tremonia ginkgo is conical in shape.
When we encounter a ginkgo tree, it should be given the respect it deserves. To have survived for more than 200 million years in basically the same form is something only a very few species living today can boast of. The ginkgo must be doing something right.
Dr. Robert Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960-1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.