Knotweed (Bian Xu)

Knotweed (Bian Xu)Compared with valuable medicinal herbs like ginseng and cordyceps, knotweed (Bian Xu) is literally such an insignificant weed, which actually is often ignored by many people even herbalists. Or, even worse, viewed as one of common invasive plant species that affect the yield of food crops, knotweed herb is being eradicated by many methods like herbicide.

Nevertheless, the ancient visionary herbalists from China had studied it fully and tried to locate its medical benefits in practice. The earliest recording of knot weed is from Shen Nong Ben Cao Jing (Agriculture God’s Canon of Materia Medica). And it was also introduced in Erya Zhu (Erya Commentary), one of the best-known textual annotations to Erya (the oldest Chinese encyclopedia known), by Guo Pu (276-324 CE).

What is knotweed?

Known as one of prostrate plants in the family of polygonum, knotweed is a close relative of Japanese Knotweed (Polygonum cuspidatum, Fallopia japonica) and He Shou Wu (Polygonum Multiflorum, Radix Polygoni Multiflori). For this reason, the name of Chinese knotweed can be pretty confusing. But in most cases, it refers to He Shou Wu rather than Bian Xu. These two Chinese herbs draw a stark contrast between, Heshouwu is so popular while knotweed unnoticed.

Medicinally it refers to the above-ground part of herbherba polygoni avicularis, which is one of annual weeds, grown mostly along roadsides in countryside. It has small pink or white flowers at internodes in early summer and fruits in fall. Knotweed shoots can be used medicinally. Stems are cylinder-shaped and slightly flat, with branches, 15 to 40cm long, and 0.2 to 0.3cm in diameter. Surface is grayish green or brownish red, with fine dense protuberant longitudinal grain. Nodes are slightly inflated, with light brown membranous ocrea, and about 3cm in length of internode. Texture is hard, easily broken, with white medulla seen in cross section. Leaves alternate, long and narrow like bamboo leaves, subsessile or shortly stipitate, deciduous or shrinking, broken, lanceolate after expansion in complete one, integrifolious, brown green or grayish green on both sides. It is odorless and slight bitter in taste. It is produced in all provinces in China.

What is it used for?

It is viewed differently from the perspective of Traditional Chinese Medicine (TCM).

Property, uses and indications

It is considered bitter and slightly cold in nature and covers meridians of urinary bladder. Thanks for the unique properties of cold descending and cold drying, this medical herb is used frequently for urinary infection and eczema clinically. Based on that, here are the main uses and indications.

(1). Promote diuresis to free strangury – damp-heat strangury, including ruinary tract infection, urinary calculus, and blood in urine, etc.;
(2). Destroy parasites to relieve itching – parasitic diseases like pinworm internally and skin conditions like sores, rash, and pruritus externally.

Usual dosage is 9 to 15 grams, in decoction.

Related Chinese herbal formulas

It is widely used in many herbal remedies and the following is the proven experiences recorded.

(1). Recorded in Sheng Sheng Bian, taking in frequent small doses of Bian Zhu decoction cures strangury;

(2). Ba Zheng San (Eight Corrections Powder), from Taiping Huimin Heji Jufang (Pharmacopoeia of the Taiping Welfare Dispensary Bureau), is used for treatments of pathogenic heat of heart channel in children or adult, accumulated toxin, dry mouth and throat, extreme thirst, fever in the face, vexation and agitation, hot and pain eyes, nosebleed, mouth ulcer, difficult painful urination or retention of urine, heat stranguria, and blood strangury. Other herbal ingredients are Che Qian Zi (Plantago Seeds), Qu Mai (Dianthus), Hua Shi (Talcum Powder), Zhi Zi (Gardenia), Gan Cao (Licorice Root), Mu Tong (Akebia Caulis), and Da Huang (Rhubarb);

(3). Included in Yao Xing Lun (Treatise on the Nature of Medicinal Herbs), its decoction was used to get rid of roundworm, manifested cardiodynia, blue in face, and foaming a t the mouth;

(4). Documented in Shi Yi Xin JIng (Core Mirror of The Dietary Doctor) by Zan Yin in Tang Dynasty, its decoction or congee was used to remove itching in lower body of children due to pinworm;

(5). Reported in Zhe Jiang Min Jing Cao Yao (Folk Herbs in Zhejiang Province), its decoction was used externally for anal itching caused by dampness and the beginning of haemorrhoids.

Potential side effects and contraindications

Now knotweed herb is getting more and more attentions and made into convenient forms to be consumed easier, like extract and supplement in pill available in most drug stores. Although the poisoning has not been previously reported, please control the daily dose between 9 to 15 grams. In addition, reportedly as one of forage grass, it is poisonous to horses and other livestock.

TCM wise, due to the bitter-cold in nature of knotweed, ancient physicians believe that taking too much of it would lead to leaking out of vital essence, and then body wasting in a long run. So, it should be avoided by those of poor constitution with body fluid deficiency and those without edema caused by heat-dampness.

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