Ginkgo biloba

Taxonomy and growth

Family

Ginkgoaceae

Genus

Ginkgo

Life cycle

perennial

Foliage

deciduous

Woodiness

woody

Growth rate

slow

Height

30 m

Spread

9 m

Fertility

Self sterile, Wind

Flower type

dioecious

Pollinators

Wind

Uses

Edible uses

Seed - raw (in small quantities), or cooked^[17]. A soft and oily texture^[16], the seed has a sweet flavour^[12][20] and tastes somewhat like a large pine nut^[17]. The baked seed makes very pleasant eating, it has a taste rather like a cross between potatoes and sweet chestnuts[K]. The seed can be boiled and used in soups, porridges etc^[10][17]. It needs to be heated before being eaten in order to destroy a mildly acrimonious principle^[19]. Another report says that the seed can be eaten raw^[5] whilst another says that large quantities of the seed are toxic^[15]. See the notes above on toxicity for more details^[17]. The raw seed is said to have a fish-like flavour^[15]. The seed is rich in niacin^[7]. It is a good source of starch and protein, but is low in fats^[17]. These fats are mostly unsaturated or monosaturated^[17]. A more detailed nutritional analysis is available^[15]. An edible oil is obtained from the seed^[12][10].

Medicinal uses

Historical medicinal uses. These records describe reported uses. They do not establish safety or effectiveness. Ask a qualified health professional before using any plant medicinally.

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^[17]. 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^[17]. They have also been shown to be effective in improving peripheral arterial circulation^[15][17] and in treating hearing disorders such as tinnitus where these result from poor circulation or damage by free radicals^[17]. The leaves contain ginkgolides, these are compounds that are unknown in any other plant species^[18]. Ginkgolides inhibit allergic responses and so are of use in treating disorders such as asthma^[18]. Eye disorders and senility have also responded to treatment^[17]. 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^[17][18]. The fruit is antibacterial, antifungal, astringent, cancer, digestive, expectorant, sedative, vermifuge^[4][6][8][9]. 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^[15]. (This report might be referring to the seed rather than the fleshy fruit[K]). The cooked seed is antitussive, astringent and sedative^[15]. It is used in the treatment of asthma, coughs with thick phlegm and urinary incontinence^[8][18]. The raw seed is said to have anticancer activity and also to be antivinous^[8][15]. It should be used with caution, however, due to reports of toxicity^[8][15]. The cooked seeds stabilize spermatogenesis^[8].

Material uses

An oil from the seed is used as a fuel in lighting^[12]. A soap substitute is produced by mixing the pulp of the seed (is the fruit meant here?) with oil or wine^[9]. Wood - light, soft, it has insect repelling qualities^[4].

Ecology and functions

Ecosystem niche

Canopy

Environment

Range

E. Asia - N. China.

Habitat

Found wild in only 2 localities at Guizhou and on the Anhui/Zhejiang border^[13], where it grows on rich sandy soils^[6].

Light

full sun

Shade tolerance

no shade

Water

moderate

Hardiness

Zone 4+

Soil textures

sandy, loamy, clay

Soil pH

acid, neutral, alkaline

Drainage

well drained

Tolerances

drought

Tolerates Nutritionally Poor Soil

No

Drought

tolerant

Propagation

Cultivation

Succeeds in most soil types so long as they are well-drained^[4][13][14], though it prefers a rather dry loam in a position sheltered from strong winds^[2]. Some of the best specimens in Britain are found growing on soils over chalk or limestone^[11]. Plants flower and fruit more reliably after hot summers or when grown in a warm sunny position^[14]. Established plants are drought resistant^[4], they also tolerate atmospheric pollution^[4][13]. Plants can grow in poor hard-packed soil, making the male forms good candidates for street planting^[16]. 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^[13]. Ginkgo is a very ornamental plant^[1][4] and there are several named forms^[2][13]. 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^[17]. It is exceptional in having motile sperm^[11] and fertilization may not take place until after the seed has fallen from the tree^[23]. This genus belongs to a very ancient order and has affinities with tree ferns and cycads^[11]. The ginkgo is usually slow growing, averaging less than 30cm per year with growth taking place from late May to the end of August^[11]. 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^[11]. 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^[5][13], have they evolved a resistance?^[5]. 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^[4]. 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^[5]. 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^[2]. Female trees have often been seen in various gardens with good crops of fruit[K]. 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^[9]. Trees can be coppiced^[13]. They can also be pruned into a fan-shape for growing on walls^[14]. Another report says that the trees dislike pruning and will often die back as a result^[18].

References

1. F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951-00-00

   ↩

2. Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. Murray 1981-00-00

   ↩1↩2↩3

3. Dirr. M. A. and Heuser. M. W. The Reference Manual of Woody Plant Propagation. Athens Ga. Varsity Press 1987-00-00 ISBN 0942375009

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4. Rosengarten. jnr. F. The Book of Edible Nuts. Walker & Co. 1984-00-00 ISBN 0802707699

   ↩1↩2↩3↩4↩5↩6↩7

5. Bianchini. F., Corbetta. F. and Pistoia. M. Fruits of the Earth.

   ↩1↩2↩3↩4

6. ? A Barefoot Doctors Manual. Running Press ISBN 0-914294-92-X

   ↩1↩2

7. Natural Food Institute, Wonder Crops. 1987.

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8. Yeung. Him-Che. Handbook of Chinese Herbs and Formulas. Institute of Chinese Medicine, Los Angeles 1985-00-00

   ↩1↩2↩3↩4↩5

9. Stuart. Rev. G. A. Chinese Materia Medica. Taipei. Southern Materials Centre

   ↩1↩2↩3

10. Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990-00-00 ISBN 0-9628087-0-9

    ↩1↩2

11. Mitchell. A. F. Conifers in the British Isles. HMSO 1975-00-00 ISBN 0-11-710012-9

    ↩1↩2↩3↩4↩5

12. Hedrick. U. P. Sturtevant's Edible Plants of the World. Dover Publications 1972-00-00 ISBN 0-486-20459-6

    ↩1↩2↩3

13. Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992-00-00 ISBN 0-333-47494-5

    ↩1↩2↩3↩4↩5↩6↩7↩8

14. Davis. B. Climbers and Wall Shrubs. Viking. 1990-00-00 ISBN 0-670-82929-3

    ↩1↩2↩3

15. Duke. J. A. and Ayensu. E. S. Medicinal Plants of China Reference Publications, Inc. 1985-00-00 ISBN 0-917256-20-4

    ↩1↩2↩3↩4↩5↩6↩7↩8

16. Elias. T. The Complete Trees of N. America. Field Guide and Natural History. Van Nostrand Reinhold Co. 1980-00-00 ISBN 0442238622

    ↩1↩2

17. Hobbs. C. Ginkgo. Elixir of Youth. Botanica Press, California. 1994-00-00 ISBN 0-9618470-3-4

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9↩10↩11↩12↩13↩14↩15

18. Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. 1995-00-00 ISBN 0-7513-020-31

    ↩1↩2↩3↩4↩5↩6

19. Schery. R. W. Plants for Man.

    ↩

20. Howes. F. N. Nuts. Faber 1948-00-00

    ↩

21. Sheat. W. G. Propagation of Trees, Shrubs and Conifers. MacMillan and Co 1948-00-00

    ↩1↩2↩3

22. McMillan-Browse. P. Hardy Woody Plants from Seed. Grower Books 1985-00-00 ISBN 0-901361-21-6

    ↩1↩2↩3↩4

23. Rushforth. K. Conifers. Christopher Helm 1987-00-00 ISBN 0-7470-2801-X

    ↩