Knotgrass

Chinese: 扁蓄

Pinyin: Biǎn Xù

Parts used: Aerial parts

TCM category: Herbs that drain Dampness

TCM nature: Cool

TCM taste(s): BitterSweet

Organ affinity: Bladder

Scientific name: Polygonum aviculare

Other names: Knotweek, birdweed, pigweed or lowgrass

Use of knotgrass (Bian Xu) in TCM

Please note that you should never self-prescribe TCM ingredients. A TCM ingredient is almost never eaten on its own but as part of a formula containing several ingredients that act together. Please consult a professional TCM practitioner, they will be best able to guide you.

Preparation: Remove roots and impurities from the plant, and leave to dry.

Dosage: 9 - 15 grams

Main actions according to TCM*: Expels Damp-Heat and encourages urination. Drains Dampness and stops itching. Kills parasites.

Primary conditions or symptoms for which knotgrass may be prescribed by TCM doctors*: Painful urination Urinary tract infection Jaundice Skin infections Itching Intestinal parasites Trichomoniasis Trich

Contraindications*: This herb should be used with caution by those with Deficient Qi.

Common TCM formulas in which knotgrass (Bian Xu) are used*

Ba Zheng San

Source date: 1107 AD

Number of ingredients: 9 herbs

Formula key actions: Clears Heat and Fire. Promotes urination. Unblocks painful urinary dribbling.

Conditions targeted*: GlomerulonephritisCystitis and others

Bian Xu is a king ingredient in Ba Zheng San. Like the name indicates, it means it has more power than other ingredients in the formula.

In Ba Zheng San, Bian Xu enters the Qi to promote urination, unblock painful urinary dribbling, and clear Damp Heat.

Read more about Ba Zheng San

Key TCM concepts behind knotgrass (Bian Xu)'s properties

In Traditional Chinese Medicine (TCM), knotgrass are plants that belong to the 'Herbs that drain Dampness' category. These herbs are typically diuretics, meaning that they promotes the increased production of urine in order to remove Dampness that has accumulated in the body. According to TCM Dampness accumulates first in the lower limbs, causing edema and impaired movement. From there, if unchecked, it can move upward and impair digestion and eventually the respiratory system.

Furthermore knotgrass are plants that are Cool in nature. This means that knotgrass tend to help people who have too much 'Heat' in their body, although with less effect than a plant that would be Cold in nature. Balance between Yin and Yang is a key health concept in TCM. Those who have too much Heat in their body are said to either have a Yang Excess (because Yang is Hot in nature) or a Yin deficiency (Yin is Cold in Nature). Depending on your condition knotgrass can help restore a harmonious balance between Yin and Yang.

Knotgrass also taste Bitter and Sweet. The so-called 'Five Phases' theory in Chinese Medicine states that the taste of TCM ingredients is a key determinant of their action in the body. Bitter ingredients like knotgrass tend to have a cleansing action on the body by clearing Heat, drying Dampness and promoting elimination via urination or bowel movements. On the other hand Sweet ingredients tend to slow down acute reactions and detoxify the body. They also have a tonic effect because they replenish Qi and Blood.

The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such knotgrass are thought to target the Bladder. In TCM the impure water collected by the Kidneys that cannot be used by the body is sent to the Bladder for storage and excretion as urine.