Fallopia japonica has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not closely related. Nodes are usually reddish in colour and stems range from green to reddish-brown during the growing season are often flecked and turn brown as they die back in winter. The stems are profusely branched and often reach a height of between 1 - 4 metres tall during the growing season though plants can be much smaller than this.
Shoots grow from underground rhizomes early in the spring. They grow rapidly and can attain full height by early summer.
The leaves are thick and tough in texture, with short petioles, broad oval with a truncated base, 7 - 14 cm long and 5 - 12 cm broad, with an entire margin. The flowers are small, cream or white, produced in erect racemes 6 - 15 cm long in late summer and early autumn.Rhizomes have an orange centre and can extend up to 7 metres from the parent plant horizontally and down 3 metres vertically
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.
An excellent source of vitamin A, along with vitamin C and the antioxidant flavonoid rutin. Provides potassium, phosphorus, zinc, and manganese. An excellent source of resveratrol which is believed to lower LDL cholesterol and reduce the risk of heart attacks.
The shoots are tart and tangy, an acid flavour that suggests comparisons with rhubarb . They can be used as subsitutes for rhubarb in pies, fruit soups, jams etc.They have also been compared to asparagus.
Shoots, very young leaves
Peeled and cooked, salted as a Vegetable
Cooked as a Vegetable
A yellow dye is obtained from the root. The plant is potentially a good source of biomass. Plants can be grown to form a ground cover that will exclude all other growth. It is best to use the sub-species compactum since this is less invasive.
The Japanese common name for F. japonica is Itadori, which can be translated as "pain puller" or "removes pain". It has a long history of use in the herbal medicine traditions of Japan, China and Korea. In Japan and China it has been used for at least 2000 years.
Extensive research has been done on the plant due to its high levels of resveratrol and its potential for treating neuro-degenerative diseases. The plant has been found to have broad antibacterial, antifungal and antiviral actions.
The root of F. japonica is antibacterial, antiviral, antischistosomal, antispriochetal, antifungal, immunostimulant, immunomodulant, anti-inflammatory, angiogensis modulator, central nervous system (brain and spinal cord) relaxant, central nervous system protectant and anti-inflammatory, antioxidant, antiathersclerotic, antihyperlipidemic, antimutagenic, anticarcinogenic, angiogenesis modulator, antineoplastic, vasodilator, antiasthmatic, inhibits platelet aggregation, inhibits eicosanoid synthesis, antithrombotic, tyrosine kinase inhibitor, oncogene inhibitor, antipyretic, cardioprotective, analgesic, antiulcer (slightly reduces stomach acid and protects against stress ulcers), hemostatic, astringent.
Called Hu zhang in traditional Chinese medicine (TCM) F. japonica is considered bitter, cold and is associated with the liver, gallbladder and lungs. It is believed to invigorate the qi and blood and stop pain, clear heat and resolve toxins, transform phlegm and stop coughs. In TCM it is used to treat arthritis, rheumatic pain, traumatic injury, jaundice, hepatitis, urinary disorders, constipation, menstrual disorders, kidney stones, gall stones, inflammation of the gallbladder (with damp heat or severe heat syndrome), trichomonas, bacterial vaginitis, hyperlipidemia, burns, hemorrhoids, carbuncles, skin infections, snake bites, dental caries.
F. japonica is considered a very important herb in the treatment of Lyme disease (Lyme borreliosis) as it specifically addresses the central nervous system and neurological complications of infection, as well as killing the Lyme bacteria itself.
F. japonica is considered a safe herb to use regularly and in relatively large doses. A toxic dose is considered to be around 75 grams for a 75kg person. Side effects of too high a dose will usually be gastrointestinal in nature - dry mouth, bitter taste in mouth, nausea, vomiting, abdominal pain, gas and bloating, abdominal distension, diarrhea. These are signs that the dosage should be reduced.
Dried, fresh, powdered, tinctured as an Antibacterial, antiviral, antischistosomal, antispriochetal, antifungal, immunostimulant, immunomodulant, anti-inflammatory, angiogensis modulator, central nervous system relaxant, central nervous system protectant and antiinflammatory, antioxidant, antiathersclerotic, antihyperlipidemic, antimutagenic, anticarcinogenic, angiogenesis modulator, antineoplastic, antirheumatic, antitussive, detoxicant, diuretic, expectorant, vasodilator, antiasthmatic, inhibits platelet aggregation, inhibits eicosanoid synthesis, antithrombotic, tyrosine kinase inhibitor, oncogene inhibitor, antipyretic, cardioprotective, analgesic, antiulcer, hemostatic, astringent, stasis eliminating, channel-deobstructant
F. japonica has been shown to not only tolerate but to also clean soils contaminated with zinc, lead and copper. It is often found growing on sites of old zinc and copper mines and alongside heavily polluted waterways. The plant removes toxins from the surrounding soil and concentrates them in its roots.
Propagation by seed may be difficult as male plants with fertile pollen are rarely found outside Japan and China. According to the Japanese Knotweed Alliance almost every plant found outside Japan [and China] is a clone from a single mother plant making F. japonica, in total biomass terms, "the biggest female in the world". F. japonica primarily reproduces by division of small pieces of root/rhizome.
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.
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.
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. 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.
Plants seem to be immune to the predations of rabbits. Often cultivated as a dye and a medicinal plant. Very closely related to P. conspicuum. Dioecious, male and female plants must be grown if seed is required.
Problems, pests & diseases
Associations & Interactions
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Polycultures & Guilds
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This table shows all the data stored for this plant.
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