EDIBLE PLANTS

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Japanese Knotweed (Fallopia japonica) - (formerly Polygonum japonica)

Japanese knotweed was introduced from Japan in 1825 as an ornamental plant. Although attractive, it has become a notoriously invasive plant. However it also has edible and medicinal properties and contains resveratrol a remarkable substance with anti ageing properties. It is also noted for attracting wildlife.

Other Names

Polygonum cuspidatum, Polygonum sieboldii, Reynoutria japonica, Fallopia japonica, Polygonum cuspidatum, Reynoutria japonica, Fleeceflower, Himalayan fleece vine, monkeyweed, Huzhang, Hancock's curse, elephant ears, pea shooters, donkey rhubarb, sally rhubarb, Japanese bamboo, American bamboo, Mexican bamboo, itadori

Japanese knotweed has been recently reclassified from the Polygonum genus to the Fallopia genus.

Hancock's Curse

The plant spread from a garden in Cornwall, England, of someone named Hancock, into the neighboring yard, causing the value of the invaded property to decrease.

Sometimes mistaken for

Sorrel, Rhubarb, Bamboo.

Edibility

Edible Parts: Leaves; Root; Seed; Stem.

Young shoots in spring - cooked. They can be used as an asparagus substitute. They have an acid flavour and can also be used as a rhubarb substitute in pies, fruit soups, jams etc. Older stems and shoot tips - cooked. They taste like a mild version of rhubarb. Seed - raw or cooked. 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. The root is sometimes eaten.

Nutritional Content Includes

Vitamin A, Vitamin C, Oxalic acid, Potassium, Phosphorus, Zinc, Manganese, Rutin, Resveratrol.

Japanese Knotweed Supplements

Resveratrol, Emodin, Huzhang root extract, He Shou Wu, Rezmelts, PureResv.

Japanese Knotweed, Medicinal Properties and Health Benefits

Always seek advice from a qualified professional before using a plant medicinally

A decoction is used in the treatment of burns, boils and abscesses, poisonous snakebites, acute hepatitis, appendicitis, traumatic injuries and menstrual irregularities. 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. It is also used in the treatment of women's complaints. Extracts of the plant have shown antitumour activity.

Resveratrol

Both Japanese knotweed and giant knotweed are important concentrated sources of resveratrol, replacing grape byproducts. Many large supplement sources of resveratrol now use Japanese knotweed and use its scientific name in the supplement labels. The plant is useful because of its year round growth and robustness in different climates

Japanese Knotweed Known Hazards

There have been reports that some plants in the same genus as Japanese knotweed (Fallopia) can cause photosensitivity in susceptible people. Many species also contain oxalic acid which can bind up other minerals. Oxalic acid is also contained in many other common foods. Cooking the leaves will reduce their content of oxalic acid. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take special caution if including this plant in their diet since it can aggravate their condition.

Cultivation details

Please read the notes on it's invasive growth habit before considering to cultivate this plant. Depending on where you live, you could be breaking the law if you cause this plant to spread. Perennial growing to 3m by 5m at a fast rate. It is hardy to zone 5. It is in flower from July to October, and the seeds ripen from August to October. The flowers are dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required) The plant is not self-fertile.

Known Legal Issues

In Britain it was made illegal to spread Japanese knotweed under the Wildlife and Countryside Act 1981. It is also classed as 'controlled waste' under the Environmental Protection Act 1990. This requires disposal at licensed landfill sites.

Invasive Growth Habit

In the U.S.A. and Europe, Japanese knotweed is widely considered an invasive species or weed. It is listed by the World Conservation Union as one of the world's 100 worst invasive species. It is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States. The success of the species has been partially attributed to its tolerance of a very wide range of soil types, pH and salinity. Its rhizomes can survive temperatures of -35 ÐC (-30 ÐF) and can extend 7 metres (23 ft) horizontally and 3 metres (9.8 ft) deep, making removal by excavation extremely difficult. The plant is also resilient to cutting, vigorously re-sprouting from the roots. The most effective method of control is by herbicide application close to the flowering stage in late summer or autumn. In some cases it is possible to eradicate Japanese knotweed in one growing season using only herbicides. Trials in the Queen Charlotte Islands (Haida Gwaii) of British Columbia using sea water sprayed on the foliage have demonstrated promising results, which may prove to be a viable option for eradication where concerns over herbicide application are too great. It can be found in 39 of the 50 United States (PUSDA) and in six provinces in Canada. The species is also common in Europe. In the U.K. it was made illegal to spread Japanese knotweed by the Wildlife and Countryside Act 1981. In the U.S.A. it is listed as an invasive weed in Ohio, Vermont, Virginia, New York, Alaska, Pennsylvania, Oregon and Washington state. Two biological pest control agents that show promise in the control of the plant are the psyllid Aphalara itadori and a leaf spot fungus from genus Mycosphaerella.

Some Other Closely Related Plants

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