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
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
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
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.