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Habitats
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Woodland Garden Sunny Edge; Cultivated Beds;
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Edible Uses
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Edible Parts: Fruit; Root.
Edible Uses:
Tuber - cooked[1, 46, 61, 105]. A floury texture[27] with a very pleasant flavour that is rather like a potato[K]. The tubers can be boiled, baked, fried, mashed, grated and added to soups[183]. They store well and for a long time[27, 37] and can also be left in the ground and harvested as required in the winter[K]. This is a top quality root crop, very suitable for use as a staple food[K]. An arrowroot can be extracted from the root[46], though this is not as good at binding other foods as the starch from D. japonica[183]. The root contains about 20% starch. 75% water, 0.1% vitamin B1, 10 - 15 mg% vitamin C[174]. Fruit. A starchy flavour, it is said to be very good for the health[206]. We wonder if this report is referring to the tubercles[K].
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Medicinal Uses
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Plants For A Future can not take any responsibility for any adverse effects from the use of plants. Always seek advice from a professional before using a plant medicinally.
Anthelmintic; Antidote; Contraceptive; Digestive; Miscellany.
The Chinese yam, called Shan Yao in Chinese herbalism, is a sweet soothing herb that stimulates the stomach and spleen and has a tonic effect on the lungs and kidneys[238]. The tuber contains allantoin, a cell-proliferant that speeds the healing process[238]. The root is an ingredient of "The herb of eight ingredients", traditionally prescribed in Chinese herbalism to treat hyperthyroidism, nephritis and diabetes[254]. The tuber is anthelmintic, digestive and gently tonic[116, 147, 218, 254]. It is used internally in the treatment of tiredness, weight loss, poor appetite, poor digestion, chronic diarrhoea, asthma, dry coughs, frequent or uncontrollable urination, diabetes and emotional instability[238]. It is applied externally to ulcers, boils and abscesses[218, 238]. The tubers are harvested in the autumn and can be used raw or baked[238]. The leaf juice is used to treat snakebites and scorpion stings[218]. The roots of most, if not all, members of this genus, contains diosgenin[222, 240]. This is widely used in modern medicine in order to manufacture progesterone and other steroid drugs. These are used as contraceptives and in the treatment of various disorders of the genitary organs as well as in a host of other diseases such as asthma and arthritis[222].
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Cultivation details
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An easily grown plant, succeeding in a fertile well-drained soil in a sunny position or light shade[27, 37, 200], though it is best in full sun[160]. Plants are hardy to at least -18°c[160]. This species of yam is much cultivated in China for its edible root which can be up to 1 metre long[1]. It has a great potential to be a commercial crop in Britain, though a satisfactory method of harvesting the root needs to be found[K]. Plants take 3 - 4 years to reach full maturity[160], though one year roots of well grown plants can weigh more than 500g. There are many cultivated forms with different root shapes in China and Japan[174]. The yam is a climbing plant that supports itself by twining around the branches of other plants[219]. It can be grown successfully into small bushes or, perhaps simpler when being grown as a root crop, it can be grown up a frame in a similar manner to growing runner beans[K]. Plants produce tubercles (small tubers that are formed in the leaf axils of the stems), and can be propagated by this means[K]. The small white flowers have a pleasant scent of cinnamon[219]. There is some confusion over the correct name for this species. One report says that D. batatas is an invalid name that is often erroneously applied to two distinct species D. opposita and D. japonica[218]. The Flora of China accepts D. batatas as a synonym for D. polystachya[266]. Dioecious. Male and female plants must be grown if seed is required.
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Propagation
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Seed - sow March to April in a sunny position in a warm greenhouse and only just cover. It germinates in 1 - 3 weeks at 20°c[175]. Prick out the seedlings as soon as they are large enough to handle and grow on in a greenhouse for their first year. Plant out in late spring as the plant comes into new growth. Basal stem cuttings in the summer[37]. Division in the dormant season, never when in growth[1]. The plant will often produce a number of shoots, the top 5 - 10 cm of the root below each shoot can be potted up to form a new plant whilst the lower part of the root can be eaten[K]. Tubercles (baby tubers) are formed in the leaf axils. These are harvested in late summer and early autumn when about the size of a pea and coming away easily from the plant. They should be potted up immediately in individual pots in an unheated greenhouse or cold frame, covering them with about 10mm of soil. Protect them from mice etc and keep the soil moist but not wet. They should come into growth in the spring, plant them out in early summer when in active growth[K].
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 You can download this page as a PDF
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Botanical References
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200266
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Links / References
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[K] Ken Fern Notes from observations, tasting etc at Plants For A Future and on field trips.
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[1]F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956
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Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaces in 1992 by a new dictionary (see [200]).
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[27]Vilmorin. A. The Vegetable Garden.
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A reprint of a nineteenth century classic, giving details of vegetable varieties. Not really that informative though.
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[37]Thompson. B. The Gardener's Assistant.
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Excellent general but extensive guide to gardening practices in the 19th century. A very good section on fruits and vegetables with many little known species.
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[46]Uphof. J. C. Th. Dictionary of Economic Plants.
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An excellent and very comprehensive guide but it only gives very short descriptions of the uses without any details of how to utilize the plants. Not for the casual reader.
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[61]Usher. G. A Dictionary of Plants Used by Man.
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Forget the sexist title, this is one of the best books on the subject. Lists a very extensive range of useful plants from around the world with very brief details of the uses. Not for the casual reader.
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[105]Tanaka. T. Tanaka's Cyclopaedia of Edible Plants of the World.
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The most comprehensive guide to edible plants I've come across. Only the briefest entry for each species, though, and some of the entries are more than a little dubious. Not for the casual reader.
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[116]Brooklyn Botanic Garden Oriental Herbs and Vegetables, Vol 39 No. 2.
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A small booklet packed with information.
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[147]? A Barefoot Doctors Manual.
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A very readable herbal from China, combining some modern methods with traditional chinese methods.
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[160]Natural Food Institute, Wonder Crops. 1987.
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Fascinating reading, this is an annual publication. Some reports do seem somewhat exaggerated though.
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[174]Kariyone. T. Atlas of Medicinal Plants.
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A good Japanese herbal.
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[175]Bird. R. (Editor) Focus on Plants. Volume 5. (formerly 'Growing from seed')
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Very readable magazine with lots of information on propagation. A good article on Corydalis spp.
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[183]Facciola. S. Cornucopia - A Source Book of Edible Plants.
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Excellent. Contains a very wide range of conventional and unconventional food plants (including tropical) and where they can be obtained (mainly N. American nurseries but also research institutes and a lot of other nurseries from around the world.
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[200]Huxley. A. The New RHS Dictionary of Gardening. 1992.
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Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
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[206]Larkcom J. Oriental Vegetables
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Well written and very informative.
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[218]Duke. J. A. and Ayensu. E. S. Medicinal Plants of China
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Details of over 1,200 medicinal plants of China and brief details of their uses. Often includes an analysis, or at least a list of constituents. Heavy going if you are not into the subject.
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[219]Grey-Wilson. C. & Matthews. V. Gardening on Walls
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A nice little book about plants for growing against walls and a small section on plants that can grow in walls.
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[222]Foster. S. & Duke. J. A. A Field Guide to Medicinal Plants. Eastern and Central N. America.
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A concise book dealing with almost 500 species. A line drawing of each plant is included plus colour photographs of about 100 species. Very good as a field guide, it only gives brief details about the plants medicinal properties.
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[238]Bown. D. Encyclopaedia of Herbs and their Uses.
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A very well presented and informative book on herbs from around the globe. Plenty in it for both the casual reader and the serious student. Just one main quibble is the silly way of having two separate entries for each plant.
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[240]Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement).
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Very terse details of medicinal uses of plants with a wide range of references and details of research into the plants chemistry. Not for the casual reader.
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[254]Chevallier. A. The Encyclopedia of Medicinal Plants
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An excellent guide to over 500 of the more well known medicinal herbs from around the world.
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[266] Flora of China
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On-line version of the Flora - an excellent resource giving basic info on habitat and some uses.
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Subject : Dioscorea batatas
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