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European olive (Olea europaea)

European Olive is widely cultivated in Australia but has become a major environmental weed in parts of temperate and humid south-eastern Australia. It can form dense, long-lived stands that crowd out native vegetation and increase bushfire risk.

Key facts

Type: Weed, tree.

Native to: Probably the Mediterranean region; its origin is difficult to determine because it has been cultivated for thousands of years..

Established in: QLD, NSW, ACT, VIC, SA, WA.

Other names: Olive, Wild Olive.

Best time to act: Seeds germinate in autumn and fruits ripen in summer; control can be undertaken throughout the year, but avoid hot periods when plants may be stressed.

Identification

  • A much-branched, evergreen shrub or tree, usually 2–10 m tall and rarely reaching 15 m, with no prickles or spines.
  • Leaves grow in opposite pairs and are narrowly oblong, 3–7 cm long and 0.8–1 cm wide, dark grey-green above and silvery-white below.
  • Cream or white flowers grow in clusters on branches arising from the bases of the leaf stalks.
  • Mature fruits are smooth, purple-black, ellipsoidal to almost round, 1.5–2.5 cm long, and contain a single stone.
  • Look-alike: African Olive (Olea europaea subsp. cuspidata) usually has larger leaves, 6–10 cm long and 1–2.5 cm wide, with a green or yellowish-brown underside; European Olive leaves are smaller and silvery-white underneath.
  • Look-alike: Australian Olive (O. paniculata) has smaller fruits, about 10 mm long, compared with 15–30 mm for European Olive.

Where it grows

In Australia it is widely naturalised in coastal and tableland areas of South Australia, Victoria and New South Wales, with a more limited distribution in southern Queensland and south-western Western Australia, particularly in areas receiving at least 500 mm of rain a year.

Why it matters

  • Dense, persistent canopies shade and crowd out other plants, prevent native regeneration, and reduce native plant abundance and diversity.
  • It can invade healthy native vegetation, including woodlands, grasslands and riverine environments, and alter woodland canopy structure.
  • Its volatile oils make the plants highly flammable and increase bushfire risk.
  • Its pollen can cause hay fever in susceptible people.

How it spreads

  • It spreads mainly by seed, dispersed by birds and other animals, including foxes and wombats.
  • Seeds can also spread through soil movement and on machinery.
  • Long-distance spread is usually through the nursery trade, with plants escaping from tree crops and gardens.

Control options

  • Use an integrated, long-term approach, choosing physical, mechanical or chemical control to suit plant size and infestation density.
  • Pull small seedlings when the soil is moist, removing the taproot; larger plants can be grubbed out or cut down.
  • Use registered herbicides on cut stumps or exposed basal parts, or use other approved methods suitable for the plant size.
  • Check treated areas for resprouting and new seedlings and continue follow-up control for many years.

Hygiene and washdown

  • Seeds can spread with soil and on machinery, so avoid moving soil or plant material from infested areas and clean soil from vehicles and equipment before leaving.
  • 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 4 of 11 regions. Regional priority weed in Central Tablelands, Greater Sydney, Hunter, North West. 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: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • 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
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources