Practical
Plants

Fallopia japonica

Japanese knotweed · Japanese bamboo · Mexican bamboo

a vegetable shrub of the Fallopia genus in the family Polygonaceae.

No photo available

Taxonomy and growth

Life cycle
perennial
Woodiness
herbaceous
Growth rate
vigorous
Height
3 m
Spread
5 m
Fertility
self sterile
Flower type
dioecious
Flower colours
white

Uses

Toxicity

Toxicity warning. The historical record reports a hazard for this plant. Do not use it to decide which parts are safe to eat or use medicinally.

Although no specific mention has been made for this species, there have been reports that some members of this genus can cause photosensitivity in susceptible people. Many species also contain oxalic acid (the distinctive lemony flavour of sorrel) - whilst not toxic this substance can bind up other minerals making them unavailable to the body and leading to mineral deficiency. Having said that, a number of common foods such as sorrel and rhubarb contain oxalic acid and the leaves of most members of this genus are nutritious and beneficial to eat in moderate quantities. Cooking the leaves will reduce their content of oxalic acid. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition[15].

Edible uses

An excellent source of vitamin A, along with vitamin C and the antioxidant flavonoid rutin. Provides potassium, phosphorus, zinc, and manganese[44][21]. An excellent source of resveratrol[25][26] which is believed to lower LDL cholesterol and reduce the risk of heart attacks[21]. The shoots are tart and tangy[21], an acid flavour that suggests comparisons with rhubarb[23][21]. They can be used as subsitutes for rhubarb in pies, fruit soups, jams etc[23][22].They have also been compared to asparagus[39][42][32][33][34][23].

Plant part
Shoots, very young leaves
Preparation
Peeled and cooked, salted
Product or use
Vegetable
Plant part
Seed
Preparation
Raw, Cooked, Ground
Product or use
Thickener, Flour

It is rather small and fiddly to utilize. The seed can also be ground into a powder and used as a flavouring and thickener in soups etc, or can be mixed with cereals when making bread, cakes etc.

Plant part
Stem
Preparation
Cooked
Product or use
Vegetable

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.

The root is antiphlogistic, bechic, depurative, diuretic, emmenagogue, emollient, febrifuge, stomachic and vulnerary[16][19][4][6][13]. It is also used in the treatment of women's complaints[4]. A decoction is used in the treatment of burn injuries, boils and abscesses, poisonous snakebites, acute hepatitis, appendicitis, traumatic injuries and menstrual irregularities[4]. The leaves can be crushed and applied externally as a poultice to abscesses, cuts etc, whilst the dried roots can be ground into a powder and applied externally[4]. Extracts of the plant have shown antitumour activity[13].

Plant part
Roots
Preparation
Dried, fresh, powdered, tinctured
Plant part
Leaves
Preparation
Crushed
Product or use
Antibacterial, astringent

Material uses

A yellow dye is obtained from the root[16][19]. The plant is potentially a good source of biomass. Plants can be grown to form a ground cover that will exclude all other growth[11]. It is best to use the sub-species compactum since this is less invasive[11].

Plant part
Whole plant
Product or use
Biomass
Plant part
Roots
Product or use
Dye

Ecology and functions

Ecosystem niche
Shrub, Herbaceous, Rhizosphere

Environment

Range
E. Asia - Japan. Commonly naturalized in S. England.
Habitat
Wet grassy places in lowland all over Japan[18].
Light
full sun
Shade tolerance
partial shade
Water
moderate
Hardiness
Zone 5+
Soil textures
sandy, loamy, clay
Soil pH
acid, neutral, alkaline
Drainage
moist
Tolerates Nutritionally Poor Soil
No
Drought
intolerant

Propagation

Seed - sow spring in a cold frame. Seed - sow spring in a cold frame. Germination is usually free and easy. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer if they have reached sufficient size. If not, overwinter them in a cold frame and plant them out the following spring after the last expected frosts. Division in spring or autumn. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.

Cultivation

A very easily grown plant, it succeeds in ordinary garden soil in sun or shade[30][31], though it prefers a moist soil in partial shade[35].

Japanese knotweed is an extremely invasive plant capable of sending up new shoots at a considerable distance from the main clump and also of growing up through tarmac[36]. It is considered to be a pest in many areas, where it is forming large clumps in the wild and out-competing native species. If grown in the garden it should be planted within a strong barrier to contain its roots. The sub-species compacta is only about 70cm tall and is far less invasive, but should still not be grown in small gardens[36].

Plants seem to be immune to the predations of rabbits[37]. Often cultivated as a dye and a medicinal plant[38][41]. Very closely related to P. conspicuum[40]. Dioecious, male and female plants must be grown if seed is required[40].

References

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

  2. Sanders. T. W. Popular Hardy Perennials. Collingridge 1926-00-00

  3. Brooklyn Botanic Garden Oriental Herbs and Vegetables, Vol 39 No. 2. Brooklyn Botanic Garden 1986-00-00

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

    ↩1↩2↩3↩4

  5. McPherson. A. and S. Wild Food Plants of Indiana. Indiana University Press 1977-00-00 ISBN 0-253-28925-4

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

    ↩

  7. Reid. B. E. Famine Foods of the Chiu-Huang Pen-ts'ao. Taipei. Southern Materials Centre 1977-00-00

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

  9. Phillips. R. & Rix. M. Perennials Volumes 1 and 2. Pan Books 1991-00-00 ISBN 0-330-30936-9

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

  11. Thomas. G. S. Plants for Ground Cover J. M. Dent & Sons 1990-00-00 ISBN 0-460-12609-1

    ↩1↩2

  12. BBC The Natural History Programme 16th September 1994. BBC 1994-00-00

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

    ↩1↩2

  14. Thomas. G. S. Perennial Garden Plants J. M. Dent & Sons, London. 1990-00-00 ISBN 0 460 86048 8

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

    ↩

  16. Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959-00-00

    ↩1↩2

  17. Harris. B. C. Eat the Weeds. Pivot Health 1973-00-00

  18. Ohwi. G. Flora of Japan. (English translation) Smithsonian Institution 1965-00-00

    ↩

  19. Usher. G. A Dictionary of Plants Used by Man. Constable 1974-00-00 ISBN 0094579202

    ↩1↩2

  20. Elias. T. and Dykeman. P. A Field Guide to N. American Edible Wild Plants. Van Nostrand Reinhold 1982-00-00 ISBN 0442222009

  21. Brill, Steve. [Knotweed] Wildman Steve Brill (2013/03/16)

    ↩1↩2↩3↩4

  22. Brill, Steve. Identifying and Harvesting Edible and Medicinal Plants: In wild (and not so wild) places. HarperCollins ISBN 0-688-11425-3 (1994/03/01)

    ↩

  23. Facciola, Stephen. Cornucopia II: A source book of edible plants. Kampong ISBN 978-0-9628087-2-2 (1999/03/01)

    ↩1↩2↩3

  24. Duke, James. [Chemicals and their Biological Activities in: Fallopia japonica] Dr. Duke's Phytochemical and Ethnobotanical Databases (2013/03/17)

  25. Buhner, Stephen Harrod. Healing Lyme: Natural healing and prevention of Lyme Borreliosis and its coinfections. Raven Press ISBN 0-9708696-3-0 (2005/03/01)

    ↩

  26. Scott, Timothy Lee. Invasive Plant Medicine: The ecological benefits and healing abilities of invasives. Healing Arts Press ISBN 978-159477305-1 (2010/03/01)

    ↩

  27. [What is Japanese Knotweed] Japanese Knotweed Alliance (2013/03/16)

  28. [Japanese Knotweed] King County, Washington (2013/03/16)

  29. [Japanese Knotweed - Fallopia japonica] Northern Ireland Environment Agency (2013/03/16)

  30. F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press (1956/01/01)

    ↩

  31. Sanders. T. W. Popular Hardy Perennials. Collingridge (1926/01/01)

    ↩

  32. Brooklyn Botanic Garden Oriental Herbs and Vegetables, Vol 39 No. 2. Brooklyn Botanic Garden (1986/01/01)

    ↩

  33. archive:PFAFimport-1599-19

    Unresolved citation

    ↩

  34. Reid. B. E. Famine Foods of the Chiu-Huang Pen-ts'ao. Taipei. Southern Materials Centre (1977/01/01)

    ↩

  35. Phillips. R. & Rix. M. Perennials Volumes 1 and 2. Pan Books ISBN 0-330-30936-9 (1991/01/01)

    ↩

  36. Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press ISBN 0-333-47494-5 (1992/01/01)

    ↩1↩2

  37. Thomas. G. S. Perennial Garden Plants J. M. Dent & Sons, London. ISBN 0 460 86048 8 (1990/01/01)

    ↩

  38. Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim (1959/01/01)

    ↩

  39. Harris. B. C. Eat the Weeds. Pivot Health (1973/01/01)

    ↩

  40. Ohwi. G. Flora of Japan. (English translation) Smithsonian Institution (1965/01/01)

    ↩1↩2

  41. Usher. G. A Dictionary of Plants Used by Man. Constable ISBN 0094579202 (1974/01/01)

    ↩

  42. Elias. T. and Dykeman. P. A Field Guide to N. American Edible Wild Plants. Van Nostrand Reinhold ISBN 0442222009 (1982/01/01)

    ↩

  43. [Japanese Knotweed] Wikipedia (2013/03/16)

  44. Workman, Dion. [Itadori (Japanese knotweed)] Shikigami (2013/03/16)

    ↩

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