Biosecurity Spotters logo

Chinese knotweed (Persicaria chinensis)

Chinese knotweed forms dense infestations that can restrict movement and smother or outcompete other plants. It can grow in native vegetation and agricultural areas in parts of New South Wales.

Key facts

Type: Weed, vine and creeper.

Native to: Asia.

Established in: NSW.

Other names: red bush.

Identification

  • It is an upright, climbing or shrubby plant with branched red stems that may have stripes or streaks.
  • As a shrub it can reach 1 metre tall, and it can grow higher when supported by other plants; stems are 70 to 100 cm long and woody at the base.
  • Leaves are smooth and soft, yellow-green with a reddish middle vein, and 4 to 15 cm long by 2 to 8 cm wide; they are oval with wavy edges and may have a darker green V-shaped spot near the base.
  • Flowers are white or pale pink, tubular or cup shaped, and grow in clusters of 1 to 3 on stalks.
  • The fruit is black, fleshy and three-sided, measuring 2.8 to 4 mm long and 2 to 3 mm wide.

Where it grows

In New South Wales it has been found in the North Coast, Hunter and Greater Sydney regions, growing along riverbanks, in forests, disturbed areas such as roadsides, and urban parks and gardens.

Why it matters

  • Dense infestations can restrict movement.
  • It smothers and outcompetes other plants.
  • It can grow in native vegetation and agricultural areas.

How it spreads

  • It spreads by seed and root fragments, and birds spread its seeds.
  • Seeds and root fragments can spread when people dump garden waste or through vehicles and machinery.

Control options

  • Seedlings and small plants may be dug out, and fruit should be disposed of carefully.
  • Contact your local council for advice on disposal.
  • Registered herbicides can be applied using spot spraying, a splatter gun, leaf wiping or basal bark treatment; follow the product label and any permit conditions.
  • For spot spraying, treat actively growing plants and cover all foliage with the herbicide mix.

Hygiene and washdown

  • Seeds and root fragments can spread on vehicles and machinery, so avoid carrying them from infested sites.
  • Do not dump garden waste that may contain seeds or root fragments.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Regional priority in 3 of 11 regions. Regional priority weed in Greater Sydney, Hunter, North Coast. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development

Sources