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Giant Knotweed

Fallopia sachalinensis

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:
4 metres tall
Riverbanks, roadsides, wasteland, waterside.

White, 5 petals
The flowers are small and borne in small clusters measuring about 10cm (4 inches) long.
3-angled seeds enclosed in a white winged papery encasing. The seeds ripen from August to October.
A perennial flower with enormous heart-shaped leaves, up to 40cm in length and 30cm wide. Similar to Japanese Knotweed but the leaves are much larger and have a heart-shaped base (not straight).
Other Names:
Sakhalin Knotweed.
Frequency (UK):
Occasionally seen  

Similar Species

Other Information


Fallopia sachalinensis, also known as giant knotweed or Sakhalin knotweed, is a species of perennial plant in the Polygonaceae family. It is native to Sakhalin island, the Kuril islands, northeastern China, and the Russian Far East. It is similar to Fallopia japonica (Japanese knotweed), but can grow to be even larger, with some reports of plants reaching up to 15 feet in height. It has large green leaves and small white or pink flowers that bloom in late summer. It is considered an invasive species in many areas and can be difficult to control once established. Due to its aggressive growth habit and ability to displace native vegetation, it is considered a major ecological threat in many parts of the world.


Giant knotweed (Fallopia sachalinensis) is a herbaceous perennial plant that belongs to the family Polygonaceae. It is native to eastern Asia, particularly the island of Sakhalin and the northern regions of Japan, but has been introduced and become invasive in many parts of the world, including Europe, North America, and New Zealand.

Giant knotweed is a large plant that can grow up to 4 meters (13 feet) in height and has stems that are thick and woody at the base. The leaves are large and heart-shaped, and can grow up to 30 cm (12 inches) in length. The flowers are small and greenish-white, and are produced in long clusters or spikes that can reach up to 50 cm (20 inches) in length.

While the plant may look attractive, it is considered to be a noxious weed in many areas, as it can quickly colonize disturbed areas, displace native plant species, and cause damage to infrastructure such as roads and buildings. It is also a threat to riparian ecosystems, where it can interfere with the natural flow of waterways and displace native aquatic species.

One of the most distinctive features of giant knotweed is its ability to spread rapidly through its extensive root system. The plant produces thick, fleshy rhizomes that can grow up to 3 meters (10 feet) in length and are capable of penetrating deeply into the soil. These rhizomes can easily spread from one area to another, making it difficult to control the plant once it becomes established.

Controlling giant knotweed can be a challenging task, as the plant is extremely resilient and can regenerate from even small fragments of its rhizomes. Mechanical methods such as digging up the plant or cutting it down can be effective, but need to be repeated multiple times in order to fully eradicate the plant. Chemical control methods can also be effective, but require the use of herbicides that may have negative impacts on non-target species and the environment.

Despite its invasive nature, giant knotweed has some potential benefits. The plant contains high levels of resveratrol, a compound that has been shown to have anti-inflammatory and antioxidant properties. Resveratrol has also been studied for its potential in treating a range of health conditions, including cancer, heart disease, and Alzheimer's disease.

While giant knotweed may have some potential health benefits, its invasive nature makes it a serious threat to native ecosystems and infrastructure. Efforts should be made to prevent the spread of this plant and to control it in areas where it has become established, in order to protect the health and biodiversity of our natural environments.

In addition to its invasive nature and potential health benefits, giant knotweed has also been used for a variety of other purposes throughout history. In Japan, the plant has been used for its edible shoots, which are harvested in the early spring and cooked in a variety of dishes. The plant has also been used in traditional Chinese medicine for its diuretic and anti-inflammatory properties.

In recent years, giant knotweed has also been investigated for its potential as a source of biofuels and as a material for construction. The plant has a high concentration of cellulose, which can be converted into ethanol through a process of fermentation. The plant's strong and durable stems have also been used in the construction of buildings and other structures.

Despite its potential uses, it is important to remember that giant knotweed is a highly invasive species that can cause significant harm to natural ecosystems. Efforts to control its spread and manage its populations should be undertaken with caution, using methods that minimize harm to non-target species and the environment.

It is also important to recognize that the spread of invasive species is often the result of human activity, such as the unintentional introduction of species through the transportation of goods and materials. By taking steps to prevent the introduction of invasive species and promoting the use of native plants in landscaping and gardening, we can help to protect the health and biodiversity of our natural environments.

One of the challenges with controlling giant knotweed is that it can quickly regenerate from small fragments of its rhizomes, making it difficult to fully eradicate the plant. As a result, it is important to take a comprehensive approach to managing giant knotweed populations, using a combination of methods that are tailored to the specific conditions and location of the infestation.

One effective method of controlling giant knotweed is through the use of biological control agents, such as insects or fungi that feed on the plant. Biological control can be an effective and environmentally friendly way to manage invasive species, but it is important to carefully consider the potential impacts on non-target species and ecosystems before introducing a new species to an area.

Another approach to controlling giant knotweed is through the use of cultural methods, such as planting native species or using mulch or other materials to suppress the growth of the plant. Cultural methods can be particularly effective in riparian ecosystems, where the natural flow of water can help to carry away plant debris and prevent the spread of rhizomes.

Finally, it is important to recognize that the spread of invasive species is often the result of broader environmental issues, such as climate change and habitat fragmentation. By addressing these underlying issues, we can help to reduce the spread and impact of invasive species like giant knotweed, and promote the health and biodiversity of our natural environments.

Distribution Map

Reproduced by kind permission of the BSBI.

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