Japanese Knotweed

(Polygonum cuspidatum)

Other Names:

(syn. Fallopia japonica, Reynoutria japonica)

Range:

Family:

Polygonaceae – Buckwheat family

Growth Type:

An invasive species, Japanese Knotweed is a tall shrub-like weed that grows in large colonies.

Height:

Can grow to 9 - 12 feet tall, although usually found much smaller

Leaves:

The leaves are spade shaped, and can be rather large. They are relatively flat at the base, and pointed at the tip, just like the end of a spade.

Stem/Trunk:

The stems are hollow with enlarged nodes, just like bamboo. During the winter, stands are easily identified as they look like stands of dried bamboo.

Root:

Rhizome

Flower Season:

Late Summer and Early Autumn

Flower Appearance:

The flowers are small, cream or white, produced in erect racemes 6–15 cm long

Seed/Fruit:

Unobserved

Miscellaneous characteristics:

An invasive species native to eastern Asia in Japan, China and Korea, which has become widespread throughout the US.

Habitat:

Disturbed soils, yards, old homesteads, roadsides

Parts Used:

Young Shoots as food. Roots for medicinal purposes.

Culinary Uses:

The young shoots can be eaten raw, or cooked. they have a sour almost rhubarb-like taste. I have heard they can be used in pies, but I have not tried this myself. Some caution should be taken when consuming this plant, as it contains oxalic acid. There is a possibility that in very large quantities oxalic acid may aggravate conditions such as rheumatism, arthritis, gout, kidney stones or hyperacidity.

Energetics

Taste: Sour
Thermal: Warming
Humidity: Drying

Traditional Medicinal Uses:

Japanese knotweed is a concentrated source of emodin, which has been used to regulate bowel function and motility. The roots of Japanese knotweed are used in traditional Chinese and Japanese herbal medicines as a natural laxative. The effective dosage has been 20 to 50 mg per day. The root has also been used in Korea to maintain oral health. It has been shown to reduce the viability of Streptococcus mutans and Streptococcus sobrinus. The roots of Polygonum cuspidatum contain Resveratrol. There have been recent studies which have shown this phenol to be effective at improving cardiac health, immune function, and supporting cognition. Here is a link to a published paper concerning the health benefits of P. cuspidatum.

Indications Citations

The fact that studies concerning all indications listed above have not yet been completed, does not mean said uses are invalid. The plants I have included have a long history of effective use, and most were part of the U.S. Pharmacopia prior to the advent of allopathic medicine.

Anti-Inflammatory: Ghanim H, Sia CL, Abuaysheh S, Korzeniewski K, Patnaik P, Marumganti A, Chaudhuri A, Dandona P. An antiinflammatory and reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum containing resveratrol. J Clin Endocrinol Metab. 2010 Sep;95(9):E1-8. doi: 10.1210/jc.2010-0482. Epub 2010 Jun 9. PMID: 20534755; PMCID: PMC2936054

Antioxidant (Renders free radicals harmless): Ghanim H, Sia CL, Abuaysheh S, Korzeniewski K, Patnaik P, Marumganti A, Chaudhuri A, Dandona P. An antiinflammatory and reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum containing resveratrol. J Clin Endocrinol Metab. 2010 Sep;95(9):E1-8. doi: 10.1210/jc.2010-0482. Epub 2010 Jun 9. PMID: 20534755; PMCID: PMC2936054

Angina (Unstable chest pain): Wu M, Yang S, Liu G, Gu C, Ren P, Zhao R, Zhao Y, Xing Y, Liu L, Liang J. Treating unstable angina with detoxifying and blood-activating formulae: A randomized controlled trial. J Ethnopharmacol. 2021 Dec 5;281:114530. doi: 10.1016/j.jep.2021.114530. Epub 2021 Aug 17. PMID: 34416295.

Atherosclerosis (Arterial Plaque build-up): Gavriil L, Detopoulou M, Petsini F, Antonopoulou S, Fragopoulou E. Consumption of plant extract supplement reduces platelet activating factor-induced platelet aggregation and increases platelet activating factor catabolism: a randomised, double-blind and placebo-controlled trial. Br J Nutr. 2019 May;121(9):982-991. doi: 10.1017/S0007114519000308. Epub 2019 Apr 3. PMID: 30940217.

Cardiovascular Disease (Cardiometabolic risk): Jarrín-Orozco MP, García-Nicolás M, Romo-Vaquero M, Carrascosa C, Berná J, Puigcerver J, Saura-Sanmartín A, Ávila-Gálvez MÁ, Espín JC. Precision health targeting TMAO in postmenopausal women: polyphenol effects modulated by urolithin A and equol metabotypes in a randomised, placebo-controlled crossover trial. Food Funct. 2026 Feb 23;17(4):2037-2049. doi: 10.1039/d5fo05461c. PMID: 41642121.

Atherosclerosis (Arterial Plaque build-up): Liu LT, Zheng GJ, Zhang WG, Guo G, Wu M. [Clinical study on treatment of carotid atherosclerosis with extraction of polygoni cuspidati rhizoma et radix and crataegi fructus: a randomized controlled trial]. Zhongguo Zhong Yao Za Zhi. 2014 Mar;39(6):1115-9. Chinese. PMID: 24956862.

Overactive Bladder Syndrome (OAB): Vecchioli-Scaldazza C, Morosetti C, Maruccia S, Casellato S, Rociola W, Illiano E, Garofalo F. A randomized, multicenter, controlled study, comparing efficacy and safety of a new complementary and alternative medicine (CAM) versus Solifenacin Succinate in women with overactive bladder syndrome. Arch Ital Urol Androl. 2017 Dec 31;89(4):296-300. doi: 10.4081/aiua.2017.4.296. PMID: 29473382.

Medicinal Actions:
Adaptogen, Antiatherosclerotic, Antibacterial, Antifungal, Anti-Inflammatory, Antimicrobic, Antineoplastic, Antioxidant, Antiviral, Aperient, Astringent, Cardiac, Cathartic, Laxative

This plant has been shown, by scientific studies, to exibit the following medicinal actions. The fact that studies concerning all of the traditional medicinal actions listed above have not yet been completed, does not mean said actions are invalid. The plants I have included have a long history of effective use, and most were part of the U.S. Pharmacopoeia prior to the rise of allopathic medicine.

Anti-Inflammatory: Ghanim H, Sia CL, Abuaysheh S, Korzeniewski K, Patnaik P, Marumganti A, Chaudhuri A, Dandona P. An antiinflammatory and reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum containing resveratrol. J Clin Endocrinol Metab. 2010 Sep;95(9):E1-8. doi: 10.1210/jc.2010-0482. Epub 2010 Jun 9. PMID: 20534755; PMCID: PMC2936054

Antioxidant (Renders free radicals harmless): Ghanim H, Sia CL, Abuaysheh S, Korzeniewski K, Patnaik P, Marumganti A, Chaudhuri A, Dandona P. An antiinflammatory and reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum containing resveratrol. J Clin Endocrinol Metab. 2010 Sep;95(9):E1-8. doi: 10.1210/jc.2010-0482. Epub 2010 Jun 9. PMID: 20534755; PMCID: PMC2936054

Antiatherosclerotic (Prevents or repairs atherosclerosis): Gavriil L, Detopoulou M, Petsini F, Antonopoulou S, Fragopoulou E. Consumption of plant extract supplement reduces platelet activating factor-induced platelet aggregation and increases platelet activating factor catabolism: a randomised, double-blind and placebo-controlled trial. Br J Nutr. 2019 May;121(9):982-991. doi: 10.1017/S0007114519000308. Epub 2019 Apr 3. PMID: 30940217

Antiatherosclerotic (Prevents or repairs atherosclerosis): Liu LT, Zheng GJ, Zhang WG, Guo G, Wu M. [Clinical study on treatment of carotid atherosclerosis with extraction of polygoni cuspidati rhizoma et radix and crataegi fructus: a randomized controlled trial]. Zhongguo Zhong Yao Za Zhi. 2014 Mar;39(6):1115-9. Chinese. PMID: 24956862.