Common Name: Maidenhair Tree

General Information

Ginkgo biloba is a deciduous tree with a crown that is conical in young trees, becoming broadly ovoid with age. It has a tall, densely branched trunk that can be up to 400cm in diameter, and can grow up to 40 metres tall[].
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.
Although widely planted as an ornamental, natural wild populations are apparently confined to a small area on Xitianmu Mt.,in Zhejiang The plant is therefore classified as 'Endangered' in the IUCN Red List of Threatened Species(1998)[].

Known Hazards

The seed contains a mildly acrimonious principle that is unstable when heated. It is therefore best to cook the seed before eating it to ensure any possible toxicity is destroyed. This acrimonious principle is probably 4'-methoxypyridoxine, which can destroy vitamin B6[]. It is more toxic for children, but the raw nuts would have to be eaten often over a period of time for the negative effects to become apparent[].
Contact with the juice of the pulp around the seed can cause minor or short-lasting irritation of the skin. Eating the pulp around the seed can cause irritation of the lips, mouth, and throat, plus stomach pain, nausea, and diarrhoea[].

Botanical References

, ,

Range

E. Asia - southeast China.

Habitat

Found wild in only 2 localities, at Guizhou and on the Anhui/Zhejiang border[], where it grows on rich sandy soils[]. Scattered in broad-leaved forests and valleys on acidic, well-drained, yellow loess; at elevations from 300 - 1,100 metres[].

Properties

Conservation Status	Endangered
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	30.00 m
Growth Rate	Slow
Pollinators	Wind
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

A very tolerant plant, it succeeds in most soil types and conditions so long as they are well-drained[, , ]. It can grow on both alkaline and acid soils, in compacted soils and in saline conditions, though it prefers a rather dry loam in a position sheltered from strong winds[, ]. Plants are found in the wild on acidic, well-drained, yellow loess soil with a pH in the range 5 - 5.5[]. 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?[].
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[].

Edible Uses

Seed - raw (in small quantities), or cooked[]. A soft and oily texture[], the seed has a sweet flavour[, ] and tastes somewhat like a large pine nut[]. The baked seed makes very pleasant eating, it has a taste rather like a cross between potatoes and sweet chestnuts[]. The seed can be boiled and used in soups, porridges etc[, ]. It needs to be heated before being eaten in order to destroy a mildly acrimonious principle[]. Another report says that the seed can be eaten raw[] whilst another says that large quantities of the seed are toxic[]. See the notes above on toxicity for more details[]. The raw seed is said to have a fish-like flavour[]. The seed is rich in niacin[]. It is a good source of starch and protein, but is low in fats[]. These fats are mostly unsaturated or monosaturated[]. A more detailed nutritional analysis is available[].

An edible oil is obtained from the seed[, ].

Medicinal

Ginkgo has a long history of medicinal use in traditional Chinese medicine, where the seed is most commonly used. These uses are mentioned in more detail later. Recent research into the plant has discovered a range of medicinally active compounds in the leaves and this has excited a lot of interest in the health-promoting potential of the plant[]. In particular, the leaves stimulate the blood circulation and have a tonic effect on the brain, reducing lethargy, improving memory and giving an improved sense of well-being[]. They have also been shown to be effective in improving peripheral arterial circulation[, ] and in treating hearing disorders such as tinnitus where these result from poor circulation or damage by free radicals[]. The leaves contain ginkgolides, these are compounds that are unknown in any other plant species[]. Ginkgolides inhibit allergic responses and so are of use in treating disorders such as asthma[]. Eye disorders and senility have also responded to treatment[]. The leaves are best harvested in the late summer or early autumn just before they begin to change colour. They are dried for later use[, ].

The fruit is antibacterial, antifungal, astringent, cancer, digestive, expectorant, sedative, vermifuge[, , , ].
The fruit is macerated in vegetable oil for 100 days and then the pulp is used in the treatment of pulmonary tuberculosis, asthma, bronchitis etc[]. (This report might be referring to the seed rather than the fleshy fruit[]).
The cooked seed is antitussive, astringent and sedative[]. It is used in the treatment of asthma, coughs with thick phlegm and urinary incontinence[, ]. The raw seed is said to have anticancer activity and also to be antivinous[, ]. It should be used with caution, however, due to reports of toxicity[, ].
The cooked seeds stabilize spermatogenesis[].

The roots are used in the treatment of leucorrhoea[].

Other Uses

An oil from the seed is used as a fuel in lighting[].

A soap substitute is produced by mixing the pulp of the seed (is the fruit meant here?) with oil or wine[].

The leaves are used for pesticides[].

Tannins are obtained from the bark[].

Wood - light, soft, it has insect repelling qualities[, ]. The wood is used for furniture making[].

Propagation

Seed - best sown as soon as it is ripe in a cold frame or in a sheltered outdoor bed[, ]. The seed requires stratification according to one report[] whilst another says that stratification is not required[] and that the seed can be sown in spring but that it must not have been allowed to dry out[]. Germination is usually good to fair. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in light shade in the greenhouse for their first year. Plant them out into their permanent positions in the following spring[, ] and consider giving them some protection from winter cold for their first winter outdoors[].
Softwood cuttings in a frame in spring[].
Cuttings of half-ripe wood, July/August in a frame. The cutting may not grow away in its first year but usually grows all right after that[].
Cuttings of mature wood, December in a frame[].