The medicinal power of Japanese knotweed

Japanese knotweed originally grows in the eastern part of Asia; in China, Korea and Japan. In North America and Europe, this perennial is a newcomer that is doing very well. It has bamboo-like trunks that can reach three meters in height. It is a nice ornamental plant, but some people complain that it is an alien species that displaces other species. In winter he retreats underground. Its root system is extensive and prepared for the cold; Japanese knotweed can tolerate a temperature of -35. In Chinese medicine it is a valued medicinal plant. NB! This article is written from the personal view of the author and may contain information that is not scientifically substantiated and/or in line with the general view.

Leaf of the Polygonum cuspidatum / Source: Jan Samanek, Wikimedia Commons (Public domain)


  • Invasive species
  • Resveratrol in Japanese knotweed
  • Naming
  • Active substances
  • Heart and vascular disease
  • Good for COPD
  • Japanese knotweed for cancer
  • Japanese knotweed for menopausal complaints
  • Dose and safety

Invasive species

Knotweed is considered an invasive species; a species that does not belong in a country or region and yet does very well there. Because people move quickly around the world and bring all kinds of plants from other parts of the world and put them in the garden, biodiversity regularly changes locally; a species is added. Botanists are concerned about this because an alien species can displace native species.

Resveratrol in Japanese knotweed

The root of Japanese knotweed is a source of resveratrol, a substance that has been shown in animal research to fight tumors. Even very rapidly spreading cancer tumors can be stopped by resveratrol. Resveratrol is able, among other things, to penetrate a cancer cell and cause this cell to kill itself, which is called apoptosis. Japanese knotweed is a good source of resveratrol. It contains more of this anti-cancer substance than peanuts and grapes. Researchers hope to soon have techniques to magnetically extract resveratrol from Japanese knotweed. Resveratrol is sold as an anti-cancer supplement.

Some naturopaths recommend daily intake of 9 to 30 grams of tea from the root of Japanese knotweed for Lyme disease, but this is not common practice in phytotherapy.


In Latin, Japanese knotweed is called Polygonum cuspidatum . Polygonum means ‘polygonal’. Cuspidatum means ‘pointing given’. It could be that it has that name because the blooms resemble pointing fingers. Polygonum is the name of several species in this family such as: viperwort, peachweed and pig grass. Many of the polygonum species have the word ‘knot’ in their name. In English this plant is called Japanese knotweed and in German it is called Japanische Staudenkn√∂terich.

Active substances

The root of Japanese knotweed is used for phytotherapeutic purposes. The main active substance in the root is resveratrol, in the forms of trans- and cis-resveratrol. Furthermore, this root contains two substances with a phytoestrogenic effect, namely: emodin and 8-0-beta-D-glucopyranoside.

Heart and vascular disease

Trans-resveratrol is a more powerful resveratrol than cis-resveratrol. A high concentration of trans-resveratrol has a strong antioxidant effect and a great anti-inflammatory effect on the walls of the blood vessels. It reduces platelet aggregation and is therefore blood thinning. Because of this effect, Japanese knotweed is good for cardiovascular diseases.

Good for COPD

COPD is an abbreviation that stands for Chronic Obstructive Pulmonary Disease. This means chronic obstructive pulmonary disease or a persistent blockage in the lungs. COPD is a collective name for several lung diseases. Japanese knotweed has an antioxidant effect, an anti-allergic function and it is anti-inflammatory. Trans-resveratrol is the most active substance in this. In addition, this medicinal plant has a resistance-enhancing effect. This reduces the frequency with which respiratory infections occur. Due to these medicinal effects, herbal therapists may decide to prescribe medications based on Japanese knotweed for:

  • COPD,
  • Bronchitis,
  • Asthma,
  • Emphysema.

Japanese knotweed for cancer

Resveratrol in Japanese knotweed has an antitumor effect. It causes tumors to eliminate themselves, which is medically called apoptosis. Furthermore, it has anti-angiogenetic activity; that is the official term for a drug that prevents the formation of blood vessels in a cancer cell. This means that the root of Japanese knotweed can be used to treat cancer.

Japanese knotweed for menopausal complaints

Resveratrol, emodin and 8-0-beta-D-glucopyranoside are good sources of phytoestrogens. These are bioidentical hormones. That is why Japanese knotweed is useful for menopausal complaints or menopausal problems. It is a phytotherapeutic agent for:

Train in Beekbergen attacked by Japanese knotweed / Source: Jaap Tamminga, Wikimedia Commons (CC BY-3.0)

  • Menopausal complaints,
  • Prevention of osteoporosis,
  • Amenorrhea or absent menstruation,
  • PMS or PreMenstrual Syndrome,
  • Dysmenorrhea or menstrual pain.

Dose and safety

For the exact dose of Japanese knotweed, you should consult a herbalist. It is a safe herb, but contact with the skin can cause a rash in a small number of people.