Identifying characteristics:
This is the only surviving species of the single genus in the ginkgo family.
The ginkgo has been on earth for a least 150 million years and is a long-lived
species-there is a tree in Korea said to be 1100 years old. Ginkgos grow
50 to 80 feet tall, but can reach 100 feet. Young trees have ascending branches
and a pyramidal shape, becoming picturesquely irregular, with large, horizontal
branches as the tree ages. Leaves
are simple and alternately arranged in clusters of 3 to 5 on spur shoots.
Margins are untoothed and the fan-shaped leaf blade is often notched at
the apex to form 2 lobes. The common name refers to the leaf shape which
is similar to that of the maidenhair fern (Adiantum sp.).
Leaf surfaces are bright green and smooth, with veins that fork into 2 equal,
parallel branches (dichotomously branched). In autumn the leaves tend to
all fall at once, forming a carpet of yellow beneath the tree. No true flowers are produced. The male and female
reproductive structures appear with the leaves in spring, on separate trees.
The "fruits" are actually
naked seeds, produced only after the female tree is 20 to 30 years old.
They are stalked, plumlike and about 1 inch in diameter. The word "ginkgo"
is derived from the Chinese words meaning "silver apricot." Each
seed consists of a nutlike center surrounded by yellow-orange flesh that
has a strong, putrid odor. The nutlike center is roasted and eaten as a
delicacy in China and Japan. This may be mildly toxic if eaten in excess,
and is poisonous if eaten raw. The small, semicircular leaf scars
each have 2 bundle scars. The buds are mounded and covered with brown,
overlapping scales. The gray-brown bark
has long, scaly ridges with darker, shallow furrows.
Similar species:
Ecology:
Distribution: Ginkgos were once native throughout the Northern Hemisphere,
but were rendered extinct in North America and Europe during the Pleistocene
Ice Age. They survived in the Yangste River valley in eastern China where
they still grow today. The ginkgo has been cultivated for centuries in China
and Japan and it is a sacred tree in the Far East. It grows well in Minnesota,
Georgia, Florida and in zones 8 and 9 of the southeast. It is a common urban
planting in many Iowa cities.
Habitat: The ginkgo is a drought-resistant, adaptable species, and is very cold hardy-thriving from zone 3 to 9. It is also very pH adaptable, tolerates air pollution and soil salt pollution, making it an ideal candidate for adverse urban conditions. Although it will grow in almost any conditions, it prefers deep, sandy, moist soil and requires full sun. It is generally resistant to insect pests and fungus attack. Some negligible leaf spot attack has been reported.
Uses:
Wood: The wood is of little value due to its scarcity. It
is lightweight, brittle, yellow and, in China and Japan, is used for chess
sets, chopping blocks and firewood. The leaves are harvested for uses as
a blood thinner and to treat circulatory illnesses. Over a million trees
are reportedly grown in one South Carolina location for commercial export
of the leaves to Europe.
Horticulture: Although a slow-grower in the Midwest, the ginkgo is a handsome, adaptable, hardy tree for use in Iowa as a specimen or in groups. It transplants well, establishes easily and is often planted in parks, arboreta and botanical gardens as a point of interest. Male cultivars are preferable, as not only is the odor of the fallen seeds unpleasant, but the abundant crops can also be very messy. Cultivars include 'Fastigiata,' a male form with an upright, columnar habit; 'Fairmont,' a narrow, pyramidal male form; and 'Shangri-la,' a fast-growing form with a compact crown and good fall color.
