Polygonum aviculare

Herbs gallery - Knotweed

Common names

  • Armstrong
  • Bian Xu
  • Cowgrass
  • Knotgrass
  • Knotweed
  • Nine Joints
  • Pigweed

Knotweed is an annually growing herb that generally grows in a horizontal position and, hence, is also often referred to as prostrate knotweed. The herb gives out stems that are unkempt and growing up to 6 inches to 12 inches in length forming a thick mat. This plant produces leaves whose shape varies from being elliptical to oval and growing up to one fourth of an inch to half an inch in length. The leaves of knotweed appear alternately from joint, also called "knot", on the stem. The plant produces minute clusters of flowers between the period of June and November. The flowers appear on the leaf axils and their color varies from light green or pink to lilac.

Knotweed is capable of claiming resources as well as overrun damaged areas prior to the growth of any other attractive grass, as this herb has early germination schedule. Since the herb knotweed is generally related to soil compaction (the process of rock formation), it can be seen growing on sidewalk edges, gravel roadbeds, paths, cervices as well as different areas where there is high-traffic, for instance in front of the goal posts of soccer fields. Knotweed has a very intricate root system and is able to dig into the most compressed soils. As aforementioned, this plant produces extremely small pinkish-white blossoms on the leaf axils. This herb propagates through its seeds. Once knotweed is well established on any place, it is extremely hard to get rid of it even with herbicides.

For over 2,000 years, Chinese herbal medicine has used knotweed as a diuretic. Similarly, in the Western convention, during the first century A.D., Greek physician Pedanius Dioscorides also regarded the knotweed as a diuretic. In addition, he also considered the herb as a medication for profuse menstrual bleeding and an antidote for snake bites.

In effect, this herb is also a food for humans and a fodder for animals. While birds are happy to feed on the seeds of knotweed, pigs as well as cattle too like this herb, hence, it is often referred to as the pigweed and cowgrass. When there is scarcity of food, even humans turn to this weed, belonging to the buckwheat family, for sustenance. They pulverize the seeds of knotweed to prepare a meal.

Parts used

Aerial parts.


Knotweed is an herb that possesses astringent and diuretic attributes and in European herbal medicine, it is used for treating diarrhea, hemorrhoids, to stop bleeding from stomach wounds, to expel worms from the body, to lessen the profuse menstrual flow as well as to stop nosebleeds. In addition, this herb is also prescribed for complaints of the pulmonary system, as the silicic acid enclosed by it facilitates to reinforce the connective tissue inside the lungs. In Chinese traditional medicine, knotweed is prescribed to people suffering from intestinal worms, for treating dysentery and diarrhea. It is also used as a diuretic, especially in cases where urination is tender.

The entire knotweed plant possesses astringent, cardio-tonic, anthelmintic (any substance that can eliminate intestinal parasites), diuretic, cholagogue (a medication that increases bile secretion), febrifuge (a medication that reduces fever), lithontripic, haemostatic (any substance that stops bleeding) as well as vulnerary (a medication that heals wounds) properties. The diuretic properties of knotweed facilitate in removing kidney stones. In recent times, a medical formulation based on alcohol has been successfully used to cure varicose veins. Generally, knotweed is harvested during summer or in the early part of autumn and is dried and stored for use as and when required.

Even the leaves of knotweed possess anthelmintic, emollient (healing) as well as diuretic properties. As aforementioned, the plant as a whole is antiphlogistic (a substance that acts against fever and/ or inflammations), anthelmintic and diuretic. The juice extracted from the knotweed plant is faintly diuretic, expectorant as well as vasoconstrictor (a medication or nerve that causes constriction of the blood vessels). When this herb is applied topically, it is an effective medication to stop nosebleed. In addition, the seeds of knotweed are known as emetic (any substance that causes vomiting) and purgative.

The knotweed plant produces a blue dye, which, in any case, is inferior to indigo. While it is yet to be ascertained which part of the plant yields the blue dye, in all probability it is the leaves of the herb. On the other hand, green and yellow dyes can be extracted from the whole plant. The roots of knotweed enclose tannins. However, the quality of tannins obtained from the plant has not been specified.

Habitat and cultivation

Knotweed is found growing in the wild in all places across the world having temperate climatic conditions. This herb grows well in open areas as well as along the shorelines. The herb and its different parts are generally harvested all through the summer.

Although knotweed thrives in the normal garden soil, it has a preference for soils that can retain moisture, but are not very fertile. In addition, knotweed grows well in full sunlight or partial shade. When cultivated in rich soils, the herb that grows in a prostrate condition may even cover an area up to one meter in diameter. While the plant has a preference for acid soils, it loathes shade. In fact, knotweed is a very common weed that has a propensity to invade cultivated ground.

For caterpillars of various species of butterflies, the knotweed is a significant food plant. In addition, the plant also produces large quantities of seeds, which are favourite food for several species of birds. It has been found that knotweed is quite immune to the preying or onslaughts of rabbits. The flowers of this herb possess very little or no odour or honey and, hence, pollinating insects seldom visit them. Therefore, the usual method of reproduction of this plant is self-fertilization. However, at times there is cross-fertilization by some insects. It may be noted that the knotweed also produces cleistogomous flowers that never open and the pollination is always done by self in the unopened flowers. This herb is very inconsistent or variable and most botanists consider it as an average species of four highly variable species.

The knotweed generally propagates by its seeds, which are sown in a cold frame in spring. The germination process of this plant is generally free and effortless. When the seedlings grow sufficiently large to be handled, prick them out individually and plant them in separate pots. The plants are subsequently planted in their permanent positions outdoors during the summer provided they have grown sufficiently large. In case the seedlings have not grown big enough, grow them in the cold frame throughout the winter and plant them in the permanent positions outdoors in the subsequent spring after the last expected frost is over.

Alternately, this herb may be propagated by division either during spring or in autumn. It is quite simple to propagate knotweed by the division method. Cut large enough divisions that can be planted directly outdoors in their permanent positions. It has been found that potting up the smaller divisions and growing them on in light shade in a cold frame is a better way of propagating this herb by the division method. Once these small divisions are well established they may be planted outdoors during the later part of spring or during early summer.


Studies undertaken by Chinese scientists hint that knotweed is effective for treating bacillary dysentery (a range of acute colon infections caused by microorganisms, particularly of the genus Shigella, that cause fever, cramps in the abdominal region and passage of blood-stained stools). As many as 104, out of 108 individuals suffering from this ailment were cured by internal use of a knotweed paste within just five days.


Chemical analysis of the knotweed has revealed that this herb encloses flavonoids, tannins, polyphenols, approximately one per cent silicic acid and mucilage.


From Dan S. - Mar-11-2014
My friend told me that the root extract of this herb helps with gum diseases. I decided to try it as I developed some swelling inside my mouth. I put some drops of this extract into a cup of warm water, stirred it carefully and started gargling. I gargled it a few times, and although the swelling didn't disappear completely, I felt very relieved. I still continue this natural treatment.