Chinese knotweed (Persicaria chinensis)
Also known as:
red bush
Chinese knotweed is an upright shrub with red stems. It can outcompete native plants.
Profile
How does this weed affect you?
Chinese knotweed is a fast-growing plant that:
- forms dense infestations that can restrict movement
- smothers and outcompetes other plants
- can grow in native vegetation and agricultural areas.
What does it look like?
Chinese knotweed is an upright, climbing or shrubby plant. As a shrub it gets to 1m tall but can grow much higher if there are other plants to support it.
Leaves are:
- yellow-green, with reddish middle vein
- smooth and soft
- 4-15 cm long and 2-8 cm wide
- oval-shaped with wavy edges
- sometimes have a darker green v-shaped spot near the base.
Flowers are:
- white or pale pink
- in clusters of 1-3 flowers
- on stalks
- tubular or cup shaped with petals joined together.
Fruit are:
- three-sided
- black and fleshy
- 2.8-4 mm long and 2-3 mm wide
Stems are:
- red with stripes or streaks
- upright or sometimes climbing
- 70-100 cm long
- woody at the base
- branched.
Chinese knotweed is an upright, vine-like, or shrubby plant. As a shrub it gets to 1m tall but can grow much higher if there are other plants to support it.
Where is it found?
Chinese knotweed has been found in the North Coast, Hunter and Greater Sydney regions.
It is native throughout Asia.
What type of environment does it grow in?
Chinese knotweed grows best in wet, tropical climates but can tolerate a range of conditions, including shade, full sun, high temperatures, salinity, drought and wet areas. It grows:
- along riverbanks
- forests
- in disturbed areas such as roadsides
- in urban areas including parks and gardens.
Maps and records
-
Recorded presence of Chinese knotweed during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
How does it spread?
Chinese knotweed spreads by both seeds and root fragment. Seeds are spread by birds. Seeds and root fragments can be spread by people dumping garden waste and via vehicles and machinery.
References
eFloras.org (nd) Flora of North America:9. Persicaria chinensis (Linnaeus) H. Gross, Bot. Jahrb. Syst. 49: 269. 1913. Retrieved 2018 from: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242100092
Galloway DJ and Lepper VE (2010). Persicaria chinensis - a new alien Asian invader? In: 17th Australasian weeds conference, SM Zydenbos (ed), New Zealand Plant Protection Society, 174-175.
PIER, Pacific Island Ecosystems at Risk (2010a). Persicaria chinensis. Weed Risk Assessment. Retreived 2/11/2023 from: http://www.hear.org/pier/wra/pacific/persicaria_chinensis_htmlwra.htm
PlantNET (The NSW Plant Information Network System) (2017). Royal Botanic Gardens and Domain Trust, Sydney. plantnet.rbgsyd.nsw.gov.au
Rojas-Sandoval, J. & Acevedo-Rodríguez, P. (2014). CABI data sheet Persicaria chinensis (Chinese knotweed). Retrieved 2/11/2023 from: https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.118915
USDA (United states department of Agriculture) (2017). Weed Risk Assessment for Persicaria chinensis (L.) H. Gross (Polygonaceae) – Chinese knotweed USDA. Retrieved 2018 from: · https://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/wra/Persicaria_chinensis_WRA.pdf
More information
Control
Physical control
Seedlings and small plants may be dug out. Dispose of fruit carefully.
Disposal
Contact your local council for advice on disposal
Chemical control
Spot spray
Spray actively growing plants. Ensure that all of the foliage is covered with the herbicide mix.
Splatter gun
Splatter guns can be used for dense infestations of weeds that are difficult to reach. The specialised nozzle produces large droplets that allow plants up to 10 m away to be sprayed with limited chance of spray drift. Spray small amounts of concentrated herbicide onto the weeds. It is not necessary to cover all of the foliage.
Leaf wiping
Wipe the herbicide mix onto the foliage. This method is suitable when Chinese know weed is growing amongst other desirable plants.
Basal bark
Spray or paint the herbicide mixture around the base of each stem from ground level up to a height of at least 30 cm from the ground. Wet the bark to the point of runoff. Old rough bark will require more spray than smooth or young thin bark. Do not apply to wet stems as this can repel the diesel or Biosafe mixture.
Herbicide options
WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
See Using herbicides for more information.
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L
(Various products)
Rate: 500 mL to 1 L per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L
(Various products)
Rate: 35 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L
(Starane™ Advanced)
Rate: 300 to 600 mL per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L
(Starane™ Advanced)
Rate: 21 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: One part product to 50 parts water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: One part product to 9 parts water
Comments: Splatter gun
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: One part product to 20 parts water
Comments: Wipe onto leaves
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg
(Various products)
Rate: 10 - 20 g per 100 L water plus surfactant
Comments: Spot spray
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High
PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg
(Various products)
Rate: 10 g per 1 L of water plus surfactant
Comments: Wipe onto leaves
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High
Biosecurity duty
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
| Area | Duty |
|---|---|
| All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
| Greater Sydney |
Regional Recommended Measure* (for Regional Priority - Eradication)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
| Hunter |
Regional Recommended Measure* (for Regional Priority - Eradication)
Notify local control authority if found. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. |
| North Coast |
Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
| *To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here |
For technical advice and assistance with identification please contact your local council weeds officer.
Reviewed 2023
