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Ray's Knotgrass

Polygonum oxyspermum

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Plant Profile

Flowering Months:
Polygonaceae (Dock)
Life Cycle:
Annual or Perennial
Maximum Size:
60 centimetres long
Beaches, fields, meadows, rocky places, sand dunes, seaside.

Variable in colour, 5 petals
The tiny green, white or pink flowers appear in auxiliary clusters of 2 to 6. Flowers have 5 petals (actually tepals).
Shiny, 3-sided, chestnut brown nutlets which develop immediately after flowering. The nutlets protrude out of the dead flowers.
More compact and larger than Common Knotgrass. The narrow leaves have pale, greyish-brown tips. Each leaf is up to 3.5cm in length and has between 3 to 6 unbranched veins.
Other Names:
Sharp-fruit Knotweed, Sharp-seeded Knotweed.
Frequency (UK):
Occasionally seen  

Similar Species

Other Information


Polygonum oxyspermum is a plant species in the Polygonaceae family. Common names for this plant include sharp-seeded knotweed and sharp-fruit knotweed. This species is native to Asia and is found in open habitats such as meadows, pastures, and rocky areas. It is a perennial herb that can grow to be up to 2 feet tall and has narrow, lance-shaped leaves. The flowers are small and white or pink, and bloom in the summer. It is not considered an invasive species in most areas.


Ray's Knotgrass, scientifically known as Polygonum oxyspermum, is a flowering plant species that belongs to the family Polygonaceae. It is an annual herb that can grow up to a height of 30-60 cm, and is commonly found in damp and marshy areas throughout the world, including Europe, Asia, North America, and Africa. The plant has a long history of use in traditional medicine, as well as in culinary and other cultural practices.

The leaves of Ray's Knotgrass are alternate, lance-shaped, and generally about 2-8 cm long. They are usually green, but may take on a reddish tint at the base. The flowers are small, greenish-white, and arranged in spike-like clusters at the end of the stems. The plant produces numerous tiny black or dark brown seeds that are around 1.5 mm in diameter.

The common name "knotgrass" comes from the Latin word "nodosus", which means knotted, and refers to the knotted appearance of the stem. The specific epithet "oxyspermum" means "sharp-seeded" in Greek, referring to the pointed shape of the seeds.

Ray's Knotgrass has been used in traditional medicine for centuries to treat a variety of ailments, including digestive problems, skin conditions, and respiratory illnesses. The plant has been found to contain a number of bioactive compounds, including flavonoids, tannins, and anthocyanins, that have antioxidant, anti-inflammatory, and antimicrobial properties. These compounds may help to reduce inflammation and oxidative stress in the body, which are linked to a number of chronic diseases, including cancer and cardiovascular disease.

In addition to its medicinal uses, Ray's Knotgrass has also been used in culinary and other cultural practices. The leaves and young shoots can be eaten raw or cooked, and are sometimes used as a substitute for spinach or sorrel. The seeds have been used as a coffee substitute, and the plant has been used to make dyes for textiles and leather.

Despite its many uses, Ray's Knotgrass is considered to be a weed in many parts of the world, as it can grow quickly and outcompete other plants in wetland habitats. However, the plant's many benefits and cultural uses make it an important species to study and conserve.

Ray's Knotgrass has been used in various traditional medicinal practices across different cultures. For instance, in Ayurvedic medicine, it is used as an astringent, diuretic, and to treat skin problems, whereas in Chinese traditional medicine, it is used to treat diarrhea and dysentery. It has also been used to treat respiratory illnesses such as asthma and bronchitis.

Research studies have shown that Ray's Knotgrass possesses potent antioxidant properties that protect against free radical damage and oxidative stress. It has also been found to have anti-inflammatory effects that may help in the treatment of various inflammatory conditions such as arthritis and inflammatory bowel disease. Moreover, some studies have shown that Ray's Knotgrass may possess anticancer properties, although more research is needed in this area.

Ray's Knotgrass can be grown easily from seed and is relatively low-maintenance, making it an attractive plant for home gardeners. It prefers damp soil and full sun to partial shade, and can be grown in containers or directly in the ground. The plant can self-seed and spread quickly, so it may need to be pruned or controlled to prevent it from taking over a garden or wetland area.

In addition to its medicinal and culinary uses, Ray's Knotgrass has also been used in traditional cultural practices. In England, it was once used as a charm against evil spirits and witches, and in France, it was used in wedding ceremonies as a symbol of fidelity and longevity. In the Netherlands, the plant was used in the production of traditional rope-making.

Ray's Knotgrass has also been studied for its potential to be used as a natural pesticide. Some of the compounds found in the plant, such as anthraquinones, have insecticidal properties that may be effective against certain pests. This could be a promising alternative to synthetic pesticides, which can have harmful effects on the environment and human health.

Furthermore, Ray's Knotgrass has been found to have phytoremediation properties. This means that the plant can absorb and remove pollutants from the soil, such as heavy metals, pesticides, and other toxic substances. This makes it a potential tool for the remediation of contaminated soil and water, particularly in wetland areas.

Ray's Knotgrass has also been used in the production of natural dyes for textiles and other materials. The plant contains anthocyanins, which are pigments that produce red, purple, and blue colors. These pigments have been extracted from the plant and used to dye wool, silk, and cotton. This could be a sustainable and environmentally friendly alternative to synthetic dyes, which can have negative impacts on the environment and human health.

In summary, Ray's Knotgrass is a versatile plant species with potential uses in medicine, food, culture, and environmental remediation. Its bioactive compounds have been found to have health benefits, and its phytoremediation properties and potential use as a natural pesticide make it an attractive option for sustainable agriculture and environmental remediation. Moreover, its cultural and historical significance adds to its value as an important plant species to study and conserve.

Distribution Map

Reproduced by kind permission of the BSBI.

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