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Mahonia (Berberis oiwakensis)

Mahonia is an introduced shrub that has established in forested gullies on the Dorrigo plateau near Bellingen. It can form dense thickets that exclude other understorey plants, so land managers should prevent its spread and remove infestations.

Key facts

Type: Weed, shrub.

Native to: Southern China, Myanmar and Taiwan.

Established in: NSW, VIC.

Other names: Chinese holly, Chinese mahonia.

Best time to act: Look for plants when the bright yellow flowers or dark berries make them easier to spot, and treat before berries can disperse.

Identification

  • It is a shrub that can grow up to 7 metres tall.
  • Its shiny, holly-like leaves can be up to 45 centimetres long, with as many as 20 pairs of leaflets.
  • The leaflets are dark green above, yellow-green below and have spiny edges.
  • Bright yellow flowers grow in clusters up to 25 centimetres long.
  • Its egg-shaped berries are purple, dark blue or almost black.
  • Look-alike: Other mahonias and holly-leaved ornamentals can look similar; the long leaves with many pairs of spiny leaflets and bright yellow flower clusters help distinguish this plant.

Where it grows

In New South Wales it has been found in canopied gullies and forests, including several clusters on the Dorrigo plateau near Bellingen.

Why it matters

  • Dense thickets can exclude other understorey vegetation.
  • It can invade forested gullies and disturb the composition of the understorey.
  • It is unpalatable to stock.

How it spreads

  • Birds can disperse seeds after eating the berries, helping the plant establish beyond planted areas.
  • Seeds can establish in suitable forest and gully habitats, so check nearby sites around known infestations.

Control options

  • For small plants, dig or pull them out and remove the root system, taking care not to spread berries or seeds.
  • For larger plants, cut the stem close to the ground and treat the stump using a herbicide method currently approved for this use in NSW.
  • Cut-stump glyphosate and picloram plus aminopyralid gel are options listed for Mahonia; always check and follow the current product label and any permit.
  • Revisit treated sites to remove regrowth and seedlings, and report infestations to the local control authority or council weeds officer.

Hygiene and washdown

  • Clean soil, berries and plant material from boots, tools, vehicles and machinery before leaving an infested site.
  • Contain removed material so berries and seeds are not carried to clean areas.
  • 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 1 of 11 regions. Regional priority weed in 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
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria

Sources