Hu Zhang

Giant Knotweed Rhizome (hu zhang, 虎杖) refers to the roots of Polygonum cuspidatum, also known as Japanese Knotweed or Mexican Bamboo. Polygonum cuspidatum is a plant in the family Polygonaceae, and it is native to China, Japan and Korea. In China, the plant is mainly found in Jiangsu, Jiangxi, Shandong, Sichuan and other places.

The plant was first introduced to Europe in the mid-19th century by a Bavarian exotic plant dealer. It was likely brought to the United States in the 1800s. Able to adapt to many different habitats and spread quickly, Polygonum cuspidatum can survive easily. The bamboo-like roots of the plant can spread up to 20 meters or more. 

With a name that means ‘Tiger Cane’ in Chinese, Hu Zhang has powerful medical properties. It has been used in Traditional Chinese Medicine (TCM) for thousands of years. The roots of Polygonum cuspidatum are usually harvested in spring and autumn, cleansed, chopped and dried under the sun for medicinal usage.

In TCM, Hu Zhang falls under the category of ‘herbs that invigorate blood’. Such herbs can stimulate blood flow and assist with the circulation of blood in cardiovascular conditions, menstrual irregularities and acute pain caused by Blood Stagnation. Cold in nature, Hu Zhang can help individuals with too much Heat in their body, such as those experiencing a Yang Excess or a Yin Deficiency, to restore a harmonious yin-yang balance.

Bitter in taste, Hu Zhang can help to cleanse the body by clearing Heat, drying Dampness and promoting elimination via urination or bowel movements. In particular, the herb targets the Liver, Lungs and gallbladder.

Traditional Chinese Medicine (TCM) shows that Hu Zhang has the following health benefits.

Hu Zhang can clear Damp-Heat from the Liver and gallbladder, and induce diuresis. This makes it an effective herb in the treatment of jaundice caused by Damp-Heat. Hu Zhang can be decocted alone or combined with other herbs such as Artemisia Capillaris (yin chen hao, 茵陳蒿), Phellodendron (huang bai, 黃栢) and Fructus Gardeniae (zhi zi, 栀子) to enhance its effectiveness in clearing Damp-Heat and alleviating jaundice. The herb can also be used to treat stranguria caused by the accumulation of Damp-Heat, manifested as difficult and painful urination, as well as leukorrhagia caused by Damp-Heat.

Hu Zhang has the actions of cooling and activating blood, clearing Heat, removing toxicity and alleviating pain. The herb can be used to treat scalds, carbuncles, swellings and sores. Also, Hu Zhang is indicated for many syndromes caused by Blood Stasis. For example, Hu Zhang can be used to treat amenorrhea and dysmenorrhea. It is also indicated for chronic arthralgia caused by qi and blood stagnation, which may result in Heat manifested as redness, swelling and painful joints.

As Hu Zhang can purge Heat, resolve phlegm and stop cough, it is also used to treat cough-related symptoms caused by Lung Heat. In addition, the herb promotes defecation. Hence, Hu Zhang is indicated for constipation due to Heat accumulation.

Modern studies suggest that Hu Zhang may help to improve cognitive abilities and manage cognitive disorders, such as Alzheimer’s disease and dementia. The resveratrol content in the herb has shown preventative effects against neurodegenerative processes that can affect neural pathways. Hu Zhang may thus help to keep brain pathways energized.

Also, Hu Zhang may help to improve blood pressure levels and prevent heart diseases. Hu Zhang may help to decrease insulin resistance while improving insulin sensitivity as well, which can aid blood sugar regulation. By reducing the strain and stress on the heart, lower blood pressure may significantly lower the risk of heart attacks and strokes by keeping the arteries and blood vessels dilated, which can prevent blood clots. The herb may also aid in cancer management. Studies have shown that resveratrol-containing foods may have chemopreventive and therapeutic effects against certain cancers.

Rich in antioxidants and antimicrobial properties, Hu Zhang may fight signs of ageing, prevent chronic diseases and reduce fungal activity. The herb may also aid weight management as it can boost metabolism and regulate oestrogen levels. Some herbalists also use Hu Zhang to reduce plaque, gum pain and gingivitis, claiming that it has anti-inflammatory properties.

Hu Zhang can be found in certain herbal stores and specialty markets. 

The recommended daily dosage of Hu Zhang is 9 -15g. It can be used externally by washing the desired area with its decoction, ground into powder for local application, consumed directly or in supplement forms.

Hu Zhang should not be used by pregnant women. Also, Hu Zhang may have estrogenic effects. This means that it may impact the effects of oestrogen replacement therapy and birth control pills. The herb may also worsen hormone-sensitive cancers, promote endometriosis or uterine fibroids.

Also, Hu Zhang contains resveratrol, an antioxidant that may slow the speed at which the liver breaks down certain medications. It can also slow blood clotting, which could increase the effects of drugs such as aspirin and warfarin.

Over-consuming Hu Zhang may cause gastrointestinal reactions, such as dry mouth, mouth pain, nausea, vomiting, abdominal pain and diarrhoea. 

We strongly encourage you to consult your healthcare provider before deciding to add Hu Zhang to your healthcare routine.

Here is a summary for Hu Zhang:

• Herb name (Chinese): 虎杖
• Herb name (Pin Yin): hǔ zhàng
• Herb name (English): Giant Knotweed Rhizome
• Herb name (Botanical): Rhizoma et Radix Polygoni Cuspidati
• Origin of species: Polygonum cuspidatum Sieb. et Zucc.
• Part(s) of herb used: Rhizome and root
• Geo-specific habitat(s): Jiangsu, Jiangxi, Shandong, Sichuan
• Taste(s) & Properties: Slightly bitter; Slightly cold; Administrates the Liver, Gall bladder and Lung Meridians
• Actions: Eases symptoms associated with jaundice, (inflammatory) urinary ailments, changes in vaginal discharge, menstrual pain or pain experienced from physical injuries; Relieves burnt or scalded skin and insect bites which trigger inflammatory conditions; Calms coughs with yellow oral discharge

Hsu, C. Y., Chan, Y. P., & Chang, J. (2007). Antioxidant activity of extract from Polygonum cuspidatum. Biological research, 40(1), 13-21. [Accessed on 11th January 2023]

Peng, W., Qin, R., Li, X., & Zhou, H. (2013). Botany, phytochemistry, pharmacology, and potential application of Polygonum cuspidatum Sieb. et Zucc.: a review. Journal of ethnopharmacology, 148(3), 729-745.[Accessed on 11th January 2023]

Zhang, H., Li, C., Kwok, S. T., Zhang, Q. W., & Chan, S. W. (2013). A review of the pharmacological effects of the dried root of Polygonum cuspidatum (Hu Zhang) and its constituents. Evidence-Based Complementary and Alternative Medicine, 2013.[Accessed on 11th January 2023]