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Pale Persicaria

Persicaria lapathifolia

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Plant Profile

Flowering Months:
Polygonaceae (Dock)
Life Cycle:
Maximum Size:
1 metre tall
Ditches, fields, gardens, meadows, riverbanks, roadsides, swamps, wasteland, waterside, wetland.

Green, 5 petals
Greenish spikes, 5 minute greenish-white petals. The flower spike is a maximum of 4 inches long.
A smooth, disc-shaped, brown or black seed (achene).
The stalked leaves are alternately arranged along the stems. They are narrowly elliptical and taper into a sharp tip. Sometimes they have a dark blotch in the centre of the leaf on the upper surface. Each leaf is up to 8cm long and 2cm wide.
Other Names:
Curlytop Knotweed, Dock-leaved Smartweed, Heart's Ease, Pale Knotweed, Pale Smartweed, Smooth Lady's Thumb, Willow Weed.
Frequency (UK):
Occasionally seen  

Other Information


Persicaria lapathifolia, commonly known as pale smartweed or smooth lady's thumb, is a species of flowering plant in the Polygonaceae family. It is native to Europe, Asia and North Africa. The plant has smooth, lance-shaped leaves and small, greenish-white flowers that grow in clusters. It typically grows in damp, disturbed areas such as ditches and wet meadows. The plant is considered an invasive weed in many parts of the world, as it can spread rapidly and outcompete native plants. It's not known to have any medicinal use and it's not recommended for any use.


Pale persicaria, scientifically known as Persicaria lapathifolia, is a herbaceous plant that belongs to the family Polygonaceae. It is a highly adaptable plant that can grow in a variety of soil types, from moist to dry, and can tolerate both sun and shade. Pale persicaria is native to Europe but has now spread to other parts of the world, including North America, Asia, and Australia.

Appearance and Habitat

Pale persicaria has an erect stem that can grow up to 1 meter in height. The stem is usually reddish or green and is covered in fine hairs. The leaves are alternate and can grow up to 15 cm in length. They are lance-shaped, have a pointed tip, and a heart-shaped base. The flowers of the pale persicaria are small, pink or white, and arranged in long, slender spikes. They bloom from July to September.

Pale persicaria can be found in a variety of habitats, including wetlands, marshes, fields, roadsides, and disturbed areas. It is considered an invasive species in some regions, where it can outcompete native vegetation.


Pale persicaria has been used for medicinal purposes for centuries. The plant contains compounds that have anti-inflammatory, antibacterial, and antifungal properties. It has been used to treat skin irritations, wounds, and infections. The plant has also been used in traditional Chinese medicine to treat diarrhea, dysentery, and other gastrointestinal problems.

In addition to its medicinal uses, pale persicaria has been used in culinary preparations. The young leaves can be used as a salad green or cooked like spinach. The seeds of the plant can also be ground into flour and used to make bread or porridge.


Despite its invasive tendencies, pale persicaria does have some ecological value. The plant is an important source of nectar for bees and other pollinators. It can also help stabilize soil in disturbed areas and prevent erosion.

However, the spread of pale persicaria can have negative impacts on native ecosystems. It can outcompete native vegetation, alter soil chemistry, and change the structure of habitats. As such, it is important to monitor and control the spread of pale persicaria in areas where it is not native.

Pale persicaria is a versatile plant with a long history of use in medicine and food. While it has some ecological benefits, its invasive tendencies mean that it can also have negative impacts on native ecosystems. As such, it is important to strike a balance between utilizing the plant's benefits and managing its potential negative impacts.

More Information about Pale Persicaria

One of the key ways to manage the spread of pale persicaria is through prevention. This includes controlling the introduction and spread of the plant through practices such as monitoring and cleaning machinery, preventing the spread of contaminated soil, and avoiding the planting of pale persicaria in gardens or landscaping.

If pale persicaria is already present in an area, management strategies may include physical removal, herbicide application, or targeted grazing by livestock. It is important to carefully consider the potential impact of these management strategies on the surrounding ecosystem before implementing them.

In addition to its ecological impact, pale persicaria can also have economic impacts. The plant can reduce crop yields and impact the quality of forage for livestock. As such, it is important for farmers and land managers to be aware of the presence of pale persicaria in their fields and take appropriate measures to control its spread.

Pale persicaria is also known to have allelopathic properties, meaning that it can release chemicals that inhibit the growth of other plants around it. This can give it a competitive advantage and further contribute to its invasive nature.

However, recent research has also shown that pale persicaria can have positive ecological impacts in certain contexts. For example, it has been found to have a symbiotic relationship with certain soil microbes, which can help increase nutrient availability in soil and improve plant growth.

The ecological impact of pale persicaria is complex and context-dependent. It is important for researchers, land managers, and policymakers to carefully consider the potential impacts of the plant on both the ecosystem and human activities before taking action to control or utilize it. This includes considering factors such as biodiversity, soil health, and economic impacts. By taking a holistic approach to managing pale persicaria, we can better understand its ecological role and make informed decisions about its management.

In addition to its medicinal and culinary uses, pale persicaria has also been used for dyeing. The plant contains a red pigment called quercitrin, which can be extracted and used to dye fabrics and fibers.

Quercitrin has also been studied for its potential antioxidant and anti-inflammatory properties. Some studies have shown that it may have beneficial effects on cardiovascular health and the immune system.

Despite its potential benefits, it is important to be cautious when using pale persicaria for medicinal purposes. The plant contains oxalates, which can cause kidney damage if consumed in large quantities. It is always recommended to consult with a healthcare professional before using any plant-based remedies.

In conclusion, pale persicaria is a plant with a complex relationship to humans and the environment. While it has been used for centuries for its medicinal and culinary properties, its invasive tendencies mean that it can have negative impacts on native ecosystems and agricultural practices. Careful management and monitoring of the plant's presence and spread are essential to striking a balance between its benefits and potential risks. Further research is also needed to better understand its ecological role and potential uses.


Pale Persicaria filmed at these locations:
  • Bolton-le-sands, Lancashire: 3rd September 2023
  • Marshside, Southport, Lancashire: 15th July 2023

Music credits
Dance of the Sugar Plum Fairy by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license.

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Distribution Map

Reproduced by kind permission of the BSBI.

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