General: The Ginkgo is a medium to large tree that reaches 20–35m tall, although some specimens in China are over 50m tall. Ginkgo trees often have angular crown and long, somewhat erratic branches. They are usually deep rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched, and the crown becomes broader as the tree ages. Some old Ginkgos produce aerial roots, known as chichi (Japanese; "nipples") or zhong-ru (Chinese), which form on the undersides of large branches and grow downwards. Chichi growth is very slow, and may take hundreds of years to occur. The function, if any, of these thick aerial roots is unknown.
Ginkgo branches grow in length by growth of shoots with regularly spaced leaves. From the axils of these leaves, "spur shoots" (also known as short shoots) develop on second-year growth. Short shoots have very short internodes (so that several years' growth may only extend them by a centimeter or two) and their leaves are ordinarily unlobed. They are short and knobby, and are arranged regularly on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, and reproductive structures are formed only on them.
The leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting), but never anastomosing to form a network. Two veins enter the leaf blade at the base and fork repeatedy in two. This is known as dichotomous venation. The leaves are 5-10 cm (rarely to 15 cm) long. The old popular name "Maidenhair tree" is because the leaves resemble some of the pinnae of the Maidenhair fern Adiantum capillus-veneris.
Leaves of long shoots are usually notched or lobed, but only from the outer surface between the veins. They are borne both on the more rapidly growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips. During summer, the leaves are a deep green, turning to brilliant yellow in the fall. They generally remain yellow for a time, then suddenly drop most of their leaves in what can seem like overnight.
For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Habitat: The ginkgo is a drought-resistant, adaptable species, and is very cold hardy thriving. It is also very pH adaptable, tolerates air pollution and soil salt pollution, making it an ideal candidate for adverse urban conditions. It will grow in almost any conditions, it prefers deep, sandy, moist soil and requires full sun.
Ginkgo is a slow-grower adaptable, hardy tree for use as a specimen or grown in groups for commercial production. 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.
Ginkgos are dioecious with separate female and male sexes. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds.
The seed is 1.5-2 cm long. Its outer layer, the sarcotesta is light yellow-brown, soft, and fruit-like. It is plum like and attractive, but the seedcoat contains butanoic acid, and smells like rancid butter when fallen on the ground. Beneath the sarcotesta is the hard sclerotesta, and a papery endotesta and nucellus.
The fertilization of ginkgo seeds is unusual in that it utilizes motile sperm; cycads are the only other seed plants with this feature. It was first discovered by the Japanese botanist Sakugoro Hirase in the early 1900s. When the pollen reaches the pollen chamber, two sperm are produced, one of which goes on to fertilize the ovule. The fertilization of ginkgo seeds is complete by the time they fall in autumn.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:100
Specimens with Barcodes:75
Species With Barcodes:1
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
The Ginkgo is disease resistance, insect-resistant wood and has the ability to form aerial roots and sprouts. This means the Ginkgo lives long, with some specimens claimed to be more than 2,500 years old; a 3,000 year-old.
Cultivars, improved and selected materials (and area of origin)
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, and Florida and in zones 8 and 9 of the southeast. It is a common urban planting in many Iowa cities.
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Relevance to Humans and Ecosystems
NOTE: Ingesting seeds may be toxic.
Commercial use: The Ginkgo 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.
Medical use: The extract from the Ginkgo leaves contains flavonoid glycosides, and ginkgolides. The extract is said to be a memory enhancer, and anti-vertigo agent. There are three effects on the human body: (1) it improves blood flow (including microcirculation in small capillaries) to most tissues and organs; (2) it protects against oxidative cell damage from free radicals (antioxidant); and (3) it blocks many of the effects of PAF (platelet aggregation, blood clotting) that have been related to the development of a number of cardiovascular, renal, respiratory and CNS (Central Nervous System) disorders.
Ginkgo is also added in small amounts to energy drinks, but it does not produce a noticeable effect, except as a placebo, or marketing tool from Ginkgo being listed on the label.
Side Effects: There are some undesirable effects of Ginkgo for individuals with blood circulation disorders, and those taking anti-coagulants (i.e., aspirin, warfarin). Recent studies have found that ginkgo has little or no effect on the anticoagulant properties or pharmacodynamics of warfarin. Ginkgo should not be used by people who are taking the anti-depressant drugs, monoamine oxidase inhibitors (MAOI) or by pregnant women. Ginkgo side effects include possible increased risk of bleeding, gastrointestinal discomfort, nausea, vomiting, diarrhea, headaches, dizziness, and restlessness. If any side effects are experienced, stop immediately taking Ginkgo supplements and consult your doctor.
Culinary use: The Ginkgo nut-like gametophytes inside the seeds are a traditional Chinese food often served at weddings. They are believed to have health benefits or have aphrodisiac qualities. Japanese cooks add Ginkgo seeds to dishes such as chawammushi, and cooked seeds are often eaten along with other dishes..
When eaten by children, in large quantities over a long period of time, the raw gametophyte (meat) of the seed can cause poisoning by MPN (4-methoxypyridoxine), which is heat-stable. Studies have demonstrated that convulsions caused by MPN can be prevented or terminated with pyridoxine. Some people are sensitive to the chemicals in the sarcotesta, the outer fleshy coating. These people should handle the seeds with care by wearing disposable gloves when preparing the seeds for consumption. The symptoms are dermatitis or blisters similar to that caused by contact with poison ivy. Seeds with the fleshy coating removed are perfectly safe to handle.
The Ginkgo is a living fossil, with fossils recognisably related to modern Ginkgo from the Permian, dating back 270 million years. The most plausible ancestral group for the order Ginkgoales is the Pteridospermatophyta, also known as the "seed ferns," specifically the order Peltaspermales. The closest living relatives of the clade are the cycads, which share with the extant G. biloba the characteristic of motile sperm. Fossils attributable to the genus Ginkgo first appeared in the Early Jurassic, and the genus diversified and spread throughout Laurasia during the middle Jurassic and Early Cretaceous. It declined in diversity as the Cretaceous progressed, and by the Paleocene, Ginkgo adiantoides was the only Ginkgo species left in the Northern Hemisphere while a markedly different (and poorly documented) form persisted in the Southern Hemisphere. At the end of the Pliocene, Ginkgo fossils disappeared from the fossil record everywhere except in a small area of central China where the modern species survived. It is doubtful whether the Northern Hemisphere fossil species of Ginkgo can be reliably distinguished. Given the slow pace of evolution and morphological similarity between members of the genus, there may have been only one or two species existing in the Northern Hemisphere through the entirety of the Cenozoic: present-day G. biloba (including G. adiantoides) and G. gardneri from the Paleocene of Scotland.
At least morphologically, G. gardneri and the Southern Hemisphere species are the only known post-Jurassic taxa that can be unequivocally recognised. The remainder may have been ecotypes or subspecies. The implications would be that G. biloba had occurred over an extremely wide range, had remarkable genetic flexibility and, though evolving genetically, never showed much speciation. While it may seem improbable that a species may exist as a contiguous entity for many millions of years, many of the Ginkgo's life-history parameters fit. These are: extreme longevity; slow reproduction rate; (in Cenozoic and later times) a wide, apparently contiguous, but steadily contracting distribution coupled with, as far as can be demonstrated from the fossil record, extreme ecological conservatism (restriction to disturbed streamside environments).
Modern-day G. biloba grows best in environments that are well-watered and drained, and the extremely similar fossil Ginkgo favored similar environments: the sediment record at the majority of fossil Ginkgo localities indicates it grew primarily in disturbed environments along streams and levees. Ginkgo therefore presents an "ecological paradox" because while it possesses some favorable traits for living in disturbed environments (clonal reproduction) many of its other life-history traits (slow growth, large seed size, late reproductive maturity) are the opposite of those exhibited by modern plants that thrive in disturbed settings.
Given the slow rate of evolution of the genus, it is possible that Ginkgo represents a pre-angiosperm strategy for survival in disturbed streamside environments. Ginkgo evolved in an era before flowering plants, when ferns, cycads, and cycadeoids dominated disturbed streamside environments, forming a low, open, shrubby canopy. Ginkgo's large seeds and habit of "bolting" - growing to a height of 10 m before elongating its side branches - may be adaptions to such an environment. The fact that diversity in the genus Ginkgo drops through the Cretaceous (along with that of ferns, cycads, and cycadeoids) at the same time that flowering plants were on the rise, supports the notion that flowering plants with better adaptations to disturbance displaced Ginkgo and its associates over time.
Ginkgo has been used for classifying plants with leaves that have more than four veins per segment, while Baiera for those with less than four veins per segment. Sphenobaiera has been used to classify plants with a broadly wedge-shaped leaf that lacks a distinct leaf stem. Trichopitys is distinguished by having multiple-forked leaves with cylindrical (not flattened) thread-like ultimate divisions; it is one of the earliest fossils ascribed to the Ginkgophyta.
- ^ Taylor, Thomas N.; Edith L. Taylor (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, NJ: Prentice Hall. pp. 138, 197. ISBN 0-13-651589-4.
- ^ "Genus: Ginkgo L.". Germplasm Resources Information Network (GRIN). United States Department of Agriculture, Agricultural Research Service, Beltsville Area. http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?4960. Retrieved 2008-03-26. "Illegal and superfluous name (Vienna ICBN Art. 52) for Ginkgo L."
- ^ Royer et al., p.84.
- ^ Royer et al., p.85.
- ^ a b Royer et al., p.91.
- ^ Royer et al., p.87.
- ^ Royer et al., p.92.
- ^ Royer et al., p.93.
- Royer, Dana L.; Hickey, Leo J.; Wing, Scott L. Ecological Conservatism in the "Living Fossil" Ginkgo. Paleobiology, (29)1, 2003, 84-104.
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