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Northern Knotgrass

Polygonum boreale

Please keep in mind that it is illegal to uproot a plant without the landowner's consent and care should be taken at all times not to damage wild plants. Wild plants should never be picked for pleasure and some plants are protected by law.
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Plant Profile

Flowering Months:
Polygonaceae (Dock)
Life Cycle:
Maximum Size:
90 centimetres tall
Beaches, fields, meadows, riverbanks, riversides, roadsides, sand dunes, seaside, wasteland, waterside, wetland.

Pink, 5 petals
White flowers, pink-edged. The flowers are slightly larger than Common Knotgrass (Polygonum aviculare). The flowers are situated at the bases of the leaves.
The fruit is an achene.
A scrambling annual flower with oblong-oval leaves.. Northern Knotgrass differs from most other species of knotgrass in that it's leaves are much larger. The leaves are short-stalked and rounded at the ends.
Other Names:
Northern Knotweed.
Frequency (UK):

Similar Species

Other Information


Polygonum boreale, commonly known as northern knotweed, is a species of flowering plant in the Polygonaceae family. It is native to North America and Canada. It is a perennial herb that typically grows to about 90 cm tall, it has a single stem or multiple stems arising from the base. The leaves are lance-shaped, glossy, and dark green. The flowers are small, greenish-white and arranged in spikes. The plant produces small, dark brown achenes that are enclosed in a persistent perianth. It prefers well-drained soils and full sun to partial shade to grow well, it is tolerant of a wide range of growing conditions, including wet soil and cold temperatures. It is often found in wetlands, meadows, and along stream banks. It is considered a medicinal plant by some indigenous people of North America.


Northern Knotgrass, scientifically known as Polygonum boreale, is a herbaceous plant species that belongs to the Polygonaceae family. It is native to the northern regions of the world, including North America, Europe, and Asia, and is commonly found in meadows, wetlands, and along riverbanks.


The Northern Knotgrass plant has slender stems that can grow up to 3 feet tall. Its leaves are narrow and lance-shaped, with a smooth surface and pointed tips. The plant's flowers are small, pink, and clustered together in a spike-like arrangement at the top of the stem. The flowers bloom from July to September and are followed by small, brown seeds.


Northern Knotgrass has a long history of medicinal use by Indigenous peoples in the regions where it grows. It is known to have anti-inflammatory, antibacterial, and antioxidant properties and has been used to treat a variety of ailments, including skin conditions, fever, and digestive issues.

In addition to its medicinal uses, Northern Knotgrass has also been used for food. Its leaves are edible and have a slightly sour taste. They can be eaten raw or cooked and are often used in salads, soups, and stews.


Northern Knotgrass is not considered a threatened species at the global level. However, in some regions, it is facing habitat loss due to urbanization and agricultural expansion. As such, it is important to take measures to conserve the plant and its habitat.

One way to protect Northern Knotgrass is to prevent the spread of invasive species that compete with it for resources. It is also important to limit human activity in areas where the plant grows, such as wetlands and riverbanks, to prevent damage to the plant and its habitat.

Northern Knotgrass is a versatile and valuable plant that has been used for centuries by Indigenous peoples in the regions where it grows. With its anti-inflammatory and antibacterial properties, it has the potential to provide a range of health benefits, and its leaves can be used as a nutritious food source.

More Information

Northern Knotgrass is a hardy plant that can grow in a variety of soil types, including wet, sandy, or clay soils. It is also tolerant of cold temperatures, making it well-suited to the northern regions where it is found.

In addition to its traditional uses in medicine and food, Northern Knotgrass has also been studied for its potential use in bioengineering and environmental remediation. Its roots have been shown to have a strong ability to bind with heavy metals in contaminated soil, making it a promising plant for phytoremediation projects.

In terms of its ecological importance, Northern Knotgrass plays a role in providing habitat for a variety of wildlife species. Its leaves and seeds are eaten by small mammals and birds, and its flowers are visited by pollinators such as bees and butterflies.

Overall, Northern Knotgrass is a valuable plant species that has a range of uses and benefits. Its hardiness and versatility make it an important plant for conservation efforts, and its potential for use in bioengineering and environmental remediation projects highlight its importance beyond traditional medicinal and culinary uses.

Distribution Map

Reproduced by kind permission of the BSBI.

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