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Lesser Knotweed

Persicaria campanulata

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:
2 metres tall
Hedgerows, riversides, roadsides, waterside.

Pink, 5 petals
Small, bell-shaped, pale pink or white flowers. The flowers appear inside branched spikes. Pink flower buds. Bluish-grey anthers.
The fruit is a 3-angled achene (type of seed).
A mat-forming, semi-evergreen perennial plant with ovate to lance-shaped leaves. The leaves are downy, up to 15cm (6 inches) long. The attractive, red leaf veins are notably prominent and grooved. The leaves are arranged together in opposite pairs up the stems. Similar in appearance to other species of Knotweed but the veins of Lesser Knotweed are distinctively grooved.
Other Names:
Bellflower Smartweed, Campanulate Knotweed, Chalk Knotweed.
Frequency (UK):
Occasionally seen  

Similar Species

Other Information


Persicaria campanulata is a species of flowering plant in the Polygonaceae family. It is also known as bellflower smartweed or campanulate knotweed. It is native to Asia and found in China, Japan and Korea. It is a perennial herb that can grow up to 2 m tall and has lanceolate leaves and small white or pink flowers that bloom in late summer. It is not considered an invasive species and is not reported to cause ecological or economic damage. This plant is used in traditional Chinese medicine for its diuretic, anti-inflammatory, and anti-bacterial properties.


Lesser knotweed, also known as Persicaria campanulata, is a herbaceous perennial plant that belongs to the family Polygonaceae. This plant is native to East Asia, including China, Japan, and Korea, but has now spread to other parts of the world, including Europe, North America, and New Zealand. Lesser knotweed has become invasive in some areas and is considered a noxious weed in some regions.

Physical Characteristics

Lesser knotweed can grow up to 6 feet tall and has a sprawling growth habit. The stems are hollow and the leaves are lance-shaped and green, with a slightly pointed tip. The flowers are small and pink or white, and they grow in clusters on spikes that emerge from the leaf axils. The plant blooms from August to October.

Ecological Impact

Lesser knotweed is a prolific seed producer, and its seeds can be dispersed by wind, water, and animals. This plant is known for its ability to quickly colonize disturbed areas, such as roadsides, abandoned fields, and riverbanks. Once established, lesser knotweed can form dense stands that outcompete native vegetation, reducing biodiversity and altering ecosystem functions. It can also cause erosion, particularly along riverbanks, as its sprawling growth habit can destabilize soil.

Control Measures

Due to its invasive nature, lesser knotweed is often targeted for control measures. However, its control can be challenging due to its prolific seed production and its ability to regrow from root fragments. There are several methods for controlling lesser knotweed, including manual removal, herbicide application, and biological control.

Manual removal involves cutting the plant down to ground level and removing as much of the root system as possible. This method can be effective for small infestations but may not be practical for larger stands.

Herbicide application can be an effective way to control lesser knotweed, particularly when used in combination with manual removal. Glyphosate-based herbicides are often used for this purpose, but care must be taken to avoid harming nearby vegetation and water sources.

Biological control involves the introduction of natural enemies, such as insects or fungi, that can attack and kill the plant. This method has been used successfully in some areas, but care must be taken to avoid unintended consequences, such as the introduction of a new invasive species.

Lesser knotweed is an invasive plant species that can have a significant impact on the environment. It is important to control its spread and prevent its establishment in new areas. If you encounter this plant in your area, it is important to report its location to your local authorities and follow any recommended control measures. By working together, we can help protect our natural ecosystems from the negative impacts of invasive species like lesser knotweed.

More Information

In addition to its negative impacts on the environment, lesser knotweed can also pose challenges for human infrastructure. Its sprawling growth habit can interfere with roads, sidewalks, and buildings, leading to costly damage and repairs. Additionally, its dense stands can impede recreational activities such as hiking and fishing, reducing the enjoyment of natural areas for humans.

Prevention is the best method for controlling the spread of lesser knotweed. It is important to be aware of its presence and take steps to prevent its introduction to new areas. This includes avoiding the purchase or planting of ornamental plants that may be contaminated with lesser knotweed seeds, cleaning equipment and vehicles that have come into contact with the plant, and properly disposing of any plant material that may contain seeds.

As with any invasive species, early detection and rapid response are key to preventing its spread. If you suspect that lesser knotweed is present in your area, it is important to report it to your local authorities as soon as possible. They can then take appropriate action to control its spread and prevent further damage to the environment and human infrastructure.

Despite the challenges associated with controlling lesser knotweed, there are several success stories of effective management of this invasive species. For example, in New Zealand, a combination of herbicide application, manual removal, and biological control has been used to successfully reduce the impact of lesser knotweed on native plant communities.

In addition to traditional control methods, there is growing interest in developing innovative solutions for managing invasive species like lesser knotweed. For example, some researchers are exploring the potential of using drones to detect and map infestations, which could improve the efficiency and accuracy of control efforts. Others are investigating the potential of using natural plant compounds to control invasive species, which could offer a more sustainable and environmentally friendly approach to management.

Public education and outreach efforts are also critical in controlling the spread of lesser knotweed and other invasive species. By raising awareness of the impacts of invasive species and providing information on how to identify and report them, we can all play a role in preventing their spread.

In conclusion, managing invasive species like lesser knotweed requires a multifaceted approach that includes prevention, early detection, and effective control measures. While the challenges associated with managing invasive species can be daunting, there are success stories and innovative solutions that offer hope for the future. By working together and staying vigilant, we can help protect our natural ecosystems from the negative impacts of invasive species like lesser knotweed.

Distribution Map

Reproduced by kind permission of the BSBI.

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