Scientific name: Persicaria elatior

Other names: Tall Knotweed


  • National: Vulnerable (EPBCA 1999)
  • Queensland: Vulnerable (NCA 1995)

What does it look like?

Knotweed is an erect herb growing 90cm tall with stalked glandular hairs with occasionally sessile glands present too. Leaves are on average 11cm long and 30mm wide and are narrow-ovate in shape. A sheath encircles the stem at the base of each leaf.

Knotweed flowers are tiny and form long narrow spikes up to 5cm long. The pink flower-segments are less than 4mm long. Flowering mostly occurs in summer. Fruits form lens-shaped nuts 2-2.5mm in length. Knotweed is a short-lived herbaceous species, with a lifespan of up to two years.

Where is it found?

The glandular knotweed ranges from the north coast of NSW to the Moreton District in South East Queensland. This herb occurs in scattered areas with little connection to other significant population locations.

Knotweed generally grows in damp sites including swamps and lakes. Sandy soils in swampy areas and riparian herb lands are key habitat elements. This herb has also been found growing along flowing watercourses, coastal swamps and occasionally in disturbed areas with little degradation.

What is threatening it?

  • Human activities and developments
  • Invasive species
  • Agricultural use.

Conservation actions

The glandular knotweed is protected under the Nature Conservation Act 1992 and the Environmental Protection and Diversity Act 1999. It is an offence to damage or interfere with the glandular knotweed in any other way than when accepted by the respective Acts.

Redland City Council manages environmental weeds throughout the Redlands Coast to minimise their impact on native ecosystems and plants such as the glandular Knotweed.

Did you know...?

After the rain, the glandular knotweed germinates readily from seed on bare ground. Knotweed grows rapidly and flowers and sets seed within six months of germinating.

On South Stradbroke Island, knotweed has been cultivated from seeds used to regenerate the species populations in the region.

How you can help

Manage environmental weeds on your property- see IndigiScapes’ brochure entitled Environmental Weeds of the Redlands [PDF, 5.0MB] or visit the centre for advice on how to remove them and stop them from spreading.

Record your sightings on the Atlas of Living Australia