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Kudzu (Pueraria lobata)

Kudzu is a highly vigorous weed that has become naturalised in the Northern Territory, Queensland and New South Wales, and on Norfolk Island. It spreads rapidly and can form extensive monocultures, threatening native ecosystems and damaging infrastructure.

Key facts

Type: Weed, vine and creeper.

Native to: Eastern and south-eastern Asia, with a natural range extending across temperate and tropical Asia and parts of the south-western Pacific..

Established in: QLD, NSW, NT.

Other names: Kudzu vine.

Identification

  • It is a perennial trailing, scrambling or climbing herb with tubers that can reach 60–90 cm long and, when old, weigh up to 180 kg.
  • Its stems can grow up to 30 m long, are densely covered in rusty hairs when young, and become almost hairless with age.
  • Leaves are divided into three leaflets, which may be lobed; the terminal leaflet is usually three-lobed and the side leaflets usually have two lobes.
  • Flowers grow in elongated clusters and are purple, violet, mauve or pink, with a bright ochre or yellow spot at the base.
  • Its flattened, rusty-haired pods are 40–130 mm long and split along two sides to release 8–15 seeds.
  • Look-alike: Blue Morning Glory (Ipomoea indica) can look similar when not flowering, but has simple leaves rather than compound leaves with three leaflets, and its leaves are usually smaller and darker.
  • Look-alike: Blue Morning Glory does not have swollen leaf-stalk bases.

Where it grows

In Australia, kudzu is found mainly in riparian zones that originally supported subtropical or dry rainforest, as well as along watercourses, roadsides, waste areas, disturbed sites and in moist forests.

Why it matters

  • Kudzu can outcompete and eliminate native plants, smothering vegetation and restricting the germination of seedlings.
  • Its growth can reduce the amount and variety of food available to native fauna and affect other habitat values.
  • It can restrict human movement, smother fences, power lines and rail lines, and reduce scenic values.
  • In the southern United States, it has infested about 3 million hectares and causes an estimated US$500 million in annual damage through lost productivity and control costs.

How it spreads

  • Kudzu spreads vegetatively when runners root at their nodes.
  • Seed dispersal is generally limited because seed production tends to be poor; seeds that are produced usually fall near the parent plant and can then be moved by water or in contaminated soil, machinery and equipment.
  • People have spread it between areas by planting it for ornamental, horticultural, erosion-control and other purposes.

Control options

  • Use registered herbicides with cut-stump, basal-bark or foliar application as appropriate to the site; larger tubers require repeated applications over at least two years.
  • Small, isolated plants can be removed by hand-pulling or digging out the tubers.
  • Pigs can help control kudzu by digging out and eating the tubers; continual cattle grazing may weaken plants and should be combined with other control methods.
  • Take care near riparian zones, wetlands and other significant environments to minimise herbicide damage to native plants and aquatic fauna.

Hygiene and washdown

  • Avoid moving contaminated soil, machinery or equipment from infested sites, as these can spread seeds.
  • 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: Restricted matter, category 3. Do not give it away, sell or release it into the environment. 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: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources