Ginkgo biloba

Ginkgo biloba, commonly known as ginkgo ( GINK-oh, -⁠goh), also known as the maidenhair tree, and often misspelled "gingko" (see Etymology below) is a species of gymnosperm tree native to East Asia. It is the last living species in the order Ginkgoales, which first appeared over 290 million years ago. Fossils similar to the living species, belonging to the genus Ginkgo, extend back to the Middle Jurassic epoch about 170 million years ago. The tree was cultivated early in human history, remains commonly planted, and is widely regarded as a living fossil. G. biloba is a long-lived, disease-resistant, dioecious tree with unique fan-shaped leaves, capable of clonal reproduction, and known for its striking yellow autumn foliage and resilience in disturbed environments. It was known historically as "silver fruit" or "white fruit" in Chinese and called "ginkgo" due to a centuries-old transcription error. It is closely related to cycads and characterized by unique seeds that resemble apricots but are not true fruits. G. biloba, once widespread but thought extinct in the wild for centuries, is now commonly cultivated in East Asia, with some genetically diverse populations possibly representing rare wild survivors in southwestern China's mountainous regions. Some G. biloba trees have survived extreme events like the Hiroshima atomic bomb. Others show extreme longevity; G. biloba specimens have been measured in excess of 1,600 years, and the largest living trees are estimated to exceed 3,500 years. Today, it is widely planted in cities worldwide for its pollution tolerance and ornamental value. G. biloba can pose health risks including potential carcinogenicity, allergic reactions, poisoning from seeds due to ginkgotoxin, drug interactions, and adverse effects such as bleeding and neurological symptoms, especially with excessive or improper use. G. biloba wood is valued for its durability and used in crafts and sake-making, while its seeds are popular in Asian cuisine despite health risks. Ginkgo-based products are widely marketed for cognitive benefits, although clinical research shows limited medical effectiveness except possibly for dementia, with approval in the European Union but not by the United States Food and Drug Administration.

Description

A large tree. It loses its leaves during the year. It grows to 24-35 m high. They are tall and upright when young and become spreading later. It can be 9 m wide. There are many branches. The small branches are of two forms - long and short. The leaves are arranged in spirals on the long branches. The green leaves are 10 cm long. They are fan shaped. They turn golden yellow in autumn. Trees are separately male and female. The reproductive structures are in clusters in the axils of the scale like leaves at the tips of the short branches. The pollen cones hang down. The ovules are on long divided fruiting stalks. Only one seed ripens on each fruiting stalk. The seeds are long and hang down on stalks. The seeds are edible and nutritious. The fruit have an unpleasant smell.

Edible Uses

The seed can be eaten raw in small quantities or cooked. It has a soft, oily texture and a sweet flavour reminiscent of a large pine nut. When baked, it tastes somewhat like a cross between potato and sweet chestnut. The seed can also be boiled and added to soups, porridges, and similar dishes. Heating is generally recommended to neutralise a mildly acrimonious principle, though one source suggests it can be eaten raw while another cautions that large quantities may be toxic. The raw seed is noted to have a fish-like flavour. Nutritionally, the seed is rich in niacin, a good source of starch and protein, and low in fats, which are mostly unsaturated or monounsaturated. Per 100 g dry weight: 403 calories; water 0%; protein 10.4 g; fat 3.3 g; carbohydrate 83 g; fibre 1.3 g; ash 3.5 g; calcium 11 mg; phosphorus 327 mg; iron 2.6 mg; sodium 15 mg; potassium 1139 mg; vitamin A 392 mg; thiamine (B1) 0.52 mg; riboflavin (B2) 0.26 mg; niacin 6.1 mg; vitamin C 54 mg. An edible oil is also obtained from the seed.

Traditional Uses

CAUTION: The seeds are poisonous if eaten raw. They should not be eaten by people on antidepressants or by pregnant women. The seeds are cooked or roasted and are edible and nutritious. They are used in both sweet and savoury dishes. The seeds are soaked in hot water to loosen the skins then roasted. They turn green. They are used in soups, stews, stir-fried dishes, and drinks. The nuts yield an edible oil.

Medicinal Uses

Ginkgo has a long history of use in traditional Chinese medicine, where the seed is most commonly employed. Research into the leaves has revealed a range of medicinally active compounds. The leaves stimulate blood circulation and have a tonic effect on the brain, reducing lethargy, improving memory, and promoting a sense of well-being. They have been shown to improve peripheral arterial circulation and to help treat hearing disorders such as tinnitus when caused by poor circulation or free radical damage. The leaves contain ginkgolides — compounds not found in any other plant species — which inhibit allergic responses and are useful in treating conditions such as asthma. Eye disorders and senility have also responded to treatment. Leaves are best harvested in late summer or early autumn, just before they begin to change colour, and dried for later use. The fruit is antibacterial, antifungal, astringent, digestive, expectorant, sedative, and vermifuge, and is also associated with cancer treatment. It is macerated in vegetable oil for 100 days, after which the pulp is used in treating pulmonary tuberculosis, asthma, and bronchitis. The cooked seed is antitussive, astringent, and sedative, used for asthma, coughs with thick phlegm, and urinary incontinence. The raw seed is reported to have anticancer activity and to be antivinous, but should be used with caution due to toxicity concerns. Cooked seeds are also used to stabilise spermatogenesis.

Known Hazards

Since 2016, G. biloba extract is classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer. When eaten in large quantities or over a long period, the seeds may cause poisoning by ginkgotoxin (4'-O-methylpyridoxine, MPN), as found in a few case reports. A heat-stable compound not destroyed by cooking, MPN may cause convulsions, which were alleviated by treatment with pyridoxine phosphate (vitamin B6), according to limited studies. Some people are sensitive to the chemicals in the sarcotesta, the outer fleshy coating. These people should handle the seeds with care, wearing disposable gloves, when preparing them for consumption. The symptoms are allergic contact dermatitis, or blisters similar to that caused by contact with poison ivy. Side effects of using ginkgo supplements may include increased risk of bleeding, gastrointestinal discomfort, nausea, vomiting, diarrhea, headaches, dizziness, heart palpitations, and restlessness. Although use of standardized Ginkgo biloba leaf extracts in moderate amounts appears to be safe, excessive use may have undesirable effects, especially in terms of drug interactions. The dosing of anticoagulants, such as warfarin or antiplatelet medication, may be adversely affected by using ginkgo supplements. According to a systemic review, the effects of ginkgo on pregnant women may include increased bleeding time, and there is inadequate information about safety during lactation. Ginkgo pollen may produce allergic reactions. Ginkgo biloba leaves and sarcotesta contain ginkgolic acids – which are highly allergenic – long-chain alkylphenols, such as bilobol or adipostatin A (bilobol is a substance related to anacardic acid from cashew nut shells and urushiols present in poison ivy and other Toxicodendron spp.) Individuals with a history of strong allergic reactions to poison ivy, mangoes, cashews and other alkylphenol-producing plants are more likely to experience an allergic reaction when consuming non-standardized ginkgo-containing preparations. The level of these allergens in standardized pharmaceutical preparations from Ginkgo biloba was restricted to 5 ppm by the Commission E of the former Federal German Health Authority. Overconsumption of seeds from Ginkgo biloba can deplete vitamin B6. Although extracts of G. biloba leaf are often marketed as cognitive enhancers, there is no evidence for effects on memory or attention in healthy people. Systematic reviews have shown there is no evidence for effectiveness of ginkgo extract in treating high blood pressure, menopause-related cognitive decline, tinnitus, post-stroke recovery, or altitude sickness. G. biloba and its extracts are not approved as a drug in the United States and do not have sufficient clinical evidence for uses as a therapy, according to a 2023 review. The United States National Center for Complementary and Integrative Health concludes that despite extensive research, ginkgo has not been conclusively proved as effective for any health condition, including dementia, cognitive decline, or other disorders for which it is commonly marketed. A 2021 umbrella review concluded that G. biloba may be useful and safe for improving cognitive function and daily living activities in people with Alzheimer's disease. A 2018 review concluded that 22- to 24-week treatment with a G. biloba extract improved behavioral and psychological symptoms of dementia, and reduced caregiver distress compared to placebo. A 2017 overview of systematic reviews concluded that G. biloba extract may modestly improve cognitive function and daily living in dementia when taken at doses over 200 mg per day for at least 22 weeks. A 2016 systematic review concluded that G. biloba extract reduced tardive dyskinesia symptoms in people with schizophrenia and is generally safe. In 2014, the Committee on Herbal Medicinal Products of the European Medicines Agency concluded that powdered ginkgo leaf extract is effective and safe for improving cognitive function and quality of life in people with mild dementia, and licensed it as a medicine in member states of the EU. Over the period 2021–2023, the US FDA issued warning letters to manufacturers of ginkgo dietary supplements for false advertising about health claims and misbranding of their products as non-approved drugs.

Distribution

It is a temperate plant. It resists pollution. It needs shelter from strong winds. It does best in deep, fertile soil. It can tolerate frost. In Melbourne Botanical Gardens. In Hobart Botanical gardens. It suits hardiness zones 3-10. Arboretum Tasmania. National Arboretum Canberra.

Where It Grows

Africa, Asia, Australia, Britain, Canada, China*, Czech Republic, East Africa, Estonia, Europe, France, Germany, Himalayas, India, Indochina, Japan, Korea, Myanmar, Nepal, Netherlands, North Africa, North America, Pakistan, Romania, Russia, SE Asia, Slovenia, South Africa, Southern Africa, Taiwan, Tasmania, Turkey, Türkiye, USA, Vietnam, Yugoslavia, Zimbabwe,

Cultivation

Succeeds in most soil types so long as they are well-drained, though it prefers a rather dry loam in a position sheltered from strong winds. Some of the best specimens in Britain are found growing on soils over chalk or limestone. Plants flower and fruit more reliably after hot summers or when grown in a warm sunny position. Established plants are drought resistant, they also tolerate atmospheric pollution. Plants can grow in poor hard-packed soil, making the male forms good candidates for street planting. Trees are often used for street planting in towns, only the males are used because the fruit from female plants has a nauseous smell. The fruit contains butanoic acid, it has the aroma of rancid butter. Ginkgo is a very ornamental plant and there are several named forms. This species is the only surviving member of a family that was believed to be extinct until fairly recent times. It has probably remained virtually unchanged for at least 150 million years and might have been growing when the dinosaurs were roaming the earth. It is exceptional in having motile sperm and fertilization may not take place until after the seed has fallen from the tree. This genus belongs to a very ancient order and has affinities with tree ferns and cycads. The ginkgo is usually slow growing, averaging less than 30cm per year with growth taking place from late May to the end of August. Growth is also unpredictable, in some years trees may not put on any new growth whilst in others there may be 1 metre of growth. This variability does not seem to be connected to water or nutrient availability. Trees are probably long-lived in Britain, one of the original plantings (in 1758) is still growing and healthy at Kew (1993). Plants are not troubled by insects or diseases, have they evolved a resistance?. Ginkgo is a popular food and medicinal crop in China, the plants are often cultivated for this purpose and are commonly grown in and around temples. Plants are either male or female, one male plant can pollinate up to 5 females. It takes up to 35 years from seed for plants to come into bearing. Prior to maturity the sexes can often be distinguished because female plants tend to have almost horizontal branches and deeply incised leaves whilst males have branches at a sharper angle to the trunk and their leaves are not so deeply lobed. Branches of male trees can be grafted onto female frees in order to fertilize them. When a branch from a female plant was grafted onto a male plant at Kew it fruited prolifically. Female trees have often been seen in various gardens with good crops of fruit. Seeds are marked by two or three longitudinal ridges, it is said that those with two ridges produce female plants whilst those with three ridges produce male plants. Trees can be coppiced. They can also be pruned into a fan-shape for growing on walls. Another report says that the trees dislike pruning and will often die back as a result. Ginkgo biloba trees are dioecious, meaning there are separate male and female trees. Male trees are preferred for planting since female trees produce fruit with a strong odour when ripe. Therefore, they are not self-fertile. Seeds are typically harvested in Autumn when they are ripe. Ginkgo trees flower in Spring, although the flowers are not very showy and are often overlooked. Ginkgo biloba is a slow to moderate grower, typically reaching a height of 20-35 meters (65-115 feet) and taking several years to establish before significant growth occurs. It may take 15-20 years to produce seeds.

Propagation

Seed is best sown as soon as ripe in a cold frame or sheltered outdoor bed. One source recommends stratification; another states it is unnecessary and that spring sowing works provided the seed has not been allowed to dry out. Germination is generally good to fair. Prick seedlings into individual pots when large enough to handle and grow on in light shade under glass for the first year. Plant out the following spring, with some protection from winter cold during the first season outdoors. Softwood cuttings can be taken in spring in a frame. Half-ripe cuttings can be taken in July or August in a frame — these may not establish in the first year but typically grow well thereafter. Mature wood cuttings can be taken in December in a frame.

Other Uses

An oil extracted from the seed is used as a fuel for lighting. Mixing the seed pulp with oil or wine produces a soap substitute. The wood is light and soft with insect-repelling properties. Ginkgo trees are also used for shade, as street trees, and as ornamental specimens; the fallen leaves can serve as soil-enriching mulch.

Production

Seedlings are grown for 3-4 years before planting out. Fruit does not appear until trees are at least 20 years old. Flowers are fertilised by free swimming male sperm which reach the ovules through a film of water. The nuts store well in the shell but only for a short time once out of the shell. Trees can live for over 1,000 years.

Other Information

The nuts are canned and sold internationally. The fruit are also sold in markets. It is cultivated.

Notes

There is only one Ginkgo species.

Nutrition

Synonyms

Also Known As

Bai guo, Icho, Dvokrpi ginko, Kaba-oo-bin, Kew tree, Pa kewo, Pa kuo, Ya-chiao-tzu, Yin xing shu

References (48)

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• Bianchini, F., Corbetta, F., and Pistoia, M., 1975, Fruits of the Earth. Cassell. p 188
• Bodkin, F., 1991, Encyclopedia Botanica. Cornstalk publishing, p 496
• Bremness, L., 1994, Herbs. Collins Eyewitness Handbooks. Harper Collins. p 57
• Brickell, C. (Ed.), 1999, The Royal Horticultural Society A-Z Encyclopedia of Garden Plants. Convent Garden Books. p 470