To celebrate our tenth anniversary, The Herb Companion sponsored the public planting of an herbal tree this summer. We’re strong and growing, and we chose as our symbol a true survivor, Ginkgo biloba, a big, beautiful, useful, hardy tree associated with memory, longevity and graceful aging.
Members of the staff of the Denver Botanic Gardens planted the 10-foot ginkgo tree for us in late July at the northeast corner of the herb garden. The next time you’re strolling through the Denver Botanic Gardens (located at 1005 York Street in east Denver), follow signs to the herb garden and look for The Herb Companion’s ginkgo near the gazebo; a marker identifies it. And stay with us over the coming years, readers, for regular reports on the progress of our birthday tree.
Ginkgos are ancient, one of the oldest tree species on Earth. The fossil record shows that its ancestors were alive 225 million years ago and that G. biloba itself has existed unchanged for perhaps 150 million years. It probably originated in eastern China but spread around the world and has been cultivated for thousands of years in the Far East. One Korean specimen is known to be 1,100 years old.
The trouble-free ginkgo tolerates heat, salt, and air pollution. Proof of the stamina and longevity of this tree was seen after the atomic bomb devastated Hiroshima in 1945. A ginkgo sprouted new leaves from its blackened stump the following spring, the only tree in the immediate area of the blast that was not killed outright. That tree is still alive today.
Ginkgo trees may grow as tall as 100 feet and as broad as 50 feet but typically are 20 to 40 feet tall in landscape plantings. They may be vase-shaped or pyramidal. The corky, furrowed gray bark contrasts attractively with the color of the fan-shaped leaves, emerald green in summer and clear yellow in fall. Unlike most trees, ginkgos drop nearly all their leaves at once in the fall. Cultivars with different forms (such as columnar, conical, weeping, and others) are available, as are forms with especially nice fall color. Ginkgos are widely used as street trees and are splendid in parks.
Ginkgo trees are either male or female. The females (if there’s a male nearby to provide pollen) produce inch-long golden fruits that smell strongly of rancid butter when they decay. In Asia, the seeds (“nuts”) from the fruits are harvested in the fall and roasted or boiled for use in soups, stir-fries, and tempura. In this country, the mess of rotting fruits seems to outweigh the value of ultimately having ginkgo nuts to snack on, so most people try to plant only male trees as landscape plants. Young male and female seedlings are indistinguishable, and they may not flower (and thus reveal their sex) until they’re twenty to fifty years old, but vegetative propagation has enabled growers to offer certifiably male trees. People who take their chances on a ginkgo seedling and end up with a female tree won’t get fruit unless there’s a male nearby.
Ginkgos are hardy in Zones 3 to 9. They prefer moist sandy soil in full sun but tolerate a wide range of soil pH. They have virtually no pests or diseases.
In China, ginkgo has traditionally been used for thousands of years to treat asthma, coughs, cancer, venereal disease, urinary incontinence, impaired hearing, respiratory disorders, and diarrhea, and to improve sexual performance. Today in Europe, where herbal medicine is more widely accepted than in the United States, ginkgo leaf extracts are among the best-selling herbal products.
Much current ginkgo research is focused on alleviating such distressing and debilitating problems of aging as stroke and Alzheimer’s disease. Modern scientific research has shown that ginkgo improves circulation of the blood by making it more fluid; impaired blood flow to the brain can adversely affect memory, concentration, and alertness. A recent study showed that ginkgo improved both short-term memory and social functioning in people with early Alzheimer’s or other dementia.
Some ginkgo components are antioxidants, neutralizing free radicals that otherwise can damage cells. Ginkgo thus may protect the retina of the eye against free-radical damage and hemorrhage due to senile macular degeneration. Other manifestations of aging that ginkgo may help include intermittent cramping and poor circulation in the legs and arthritis.
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