Plant of the Week
Latin: Ginkgo biloba
On my desk sits a fossilized ginkgo leaf from the badlands of North Dakota. The ginkgo tree that produced the leaf grew in a then-subtropical region just after the extinction of the dinosaurs during the Lower Paleocene about 65 million years ago. Ginkgos first appeared in the fossil record about 290 million years ago just after the earth’s coal and oil deposits were laid down.
Ginkgo (Ginkgo biloba) is a monotypic tree with few close relatives in the plant kingdom. It’s a deciduous gymnosperm classified alone in its own family and is more closely related to cycads than pines. It produces motile male spores which swim to the female ovules in a film of water much as in primitive plant forms such as ferns.
Ginkgos are capable of growing to 100 feet tall or more with the growth form varying considerably between trees. The best have oval to pyramidal crowns with regular ascending branches. Poorly shaped seedlings often have ascending limbs with little lateral branching and create gawky, ungraceful specimens. Ginkgos produce two kinds of branches; long shoots and short shoots (spurs). Trees can live to great age with specimens over 1,000 years old not uncommon in China.
The triangular, fan-shaped leaves have prominent veins running the length of the leaf. The leaves are borne at nodes along the stem, but because the nodes of the short shoots are so constricted, they appear to cluster at the ends of the short shoots. In the fall, the leaves turn a beautiful golden yellow and are one of the most dependable plants for producing striking fall color effect. When the leaves decide to fall they more or less drop all at the same time.
Ginkgos are either male or female. We horticulturists are supposed to only recommend planting named male clones because the fleshy yellow fruit produced on female trees are a bit stinky, reminiscent of fresh dog poop. But each “fruit” produces a big, supposedly edible seed. Frank Meyer, the USDA plant explorer who traveled throughout China 100 years ago, described the roasted seeds as not tasting much better than they smelled.
Though now much renowned, ginkgo was relatively unknown in China until the Song Dynasty about 1000 years ago. After that time it was introduced to Japan where a physician, Engelbert Kaempfer, working for the Dutch East India Company first saw it in 1690. He described it in his 1712 book. The oldest documented ginkgo in the United States is the male tree growing in the Woodlands Cemetery in West Philadelphia which was planted in 1784.
Any species that can survive for almost 300 million years must be tough. Not only did ginkgos survive the extinctions that followed our planet’s collision with a giant meteorite, at least five ginkgos within a 1-mile radius of the1945 A-bomb blast at Hiroshima still survive. This is one tough tree.
Every park, schoolyard and public gathering place should have a ginkgo, but its slow growth makes it an unwise choice for shading the patio. Ginkgos are adaptable to a wide range of soil conditions. They tolerate a wide range of soil pH conditions and are especially heat tolerant. The species is especially tolerant of air pollution and is often used as a street tree in our most polluted cities. It is essentially free of insect and disease pests.
How fast do ginkgos grow? A tree I grew from seed planted in 1978 is now about 20 feet tall with a 6-inch diameter trunk. It averaged about 8 inches a year; others report trees averaging from 5 to 13 inches per annum. The largest ginkgo I know of in Arkansas is a 75-foot tall specimen growing in Pine Bluff with a trunk diameter of 4 ½ feet.
By: Gerald Klingaman, retired
Extension Horticulturist - Ornamentals
Extension News - December 14, 2007
The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.