Quick Facts

Quick facts

• Originally from Southern Europe and cultivation, European Olive (Olea europaea subsp. europaea) is an evergreen shrub or tree,with  narrowly linear- oblong leaves 3–7 cm long and 0.8–1 cm wide, dark grey-green above, and silvery to white below with a pointed leaf-tip.
• Cultivated for its edible, and oil bearing fruits.
• European Olive is highly invasive can form dense thickets in parkland or bushland where it crowds out other species.
• European Olive is common in South Australia and Victoria, with fewer records from Western Australia,  New South Wales and Queensland.
• It has become naturalised in many areas of southern Australia that receive at least 500 mm rainfall per year, tolerant of long summer droughts.
• Can establish in undisturbed pristine native vegetation, over decades forming dense populations excluding native plants and animals.
• It is locally dispersed by birds and animals, mostly introduced pests, and more widely through the nursery trade, and plantations.
• Can be controlled by physical and mechanical means, herbicides with many techniques used depending on age and density of plants.
• Control of established populations requires integrated techniques over many years.

What Does It Look Like?

What is it?

European Olive (Olea europaea subsp. europaea) is a much branched evergreen shrub or tree, 2–10 (rarely 15) m high, without prickles or spines. The leaves grow in pairs along the branches. They are narrowly linear-oblong to linear-oval, 3–7 cm long and 0.8–1 cm wide, dark grey-green above, and silvery to white below due to covering of short hairs. The edges of the leaf curl back, the leaf-base narrows gradually to wedge-shaped, the leaf-tip is pointed, and the main venation (mid-rib) obvious on upper surface with some lateral veins just visible. The leaf stalks are up to 10 mm long.

Flowers are cream or white in colour borne in many-flowered clusters on branches 5–6 cm long, which arise from the base of the leaf stalks. Each flower is small, with four petals, 4–5 mm long with a tube 1–2 mm long, with lobes c. 3 mm long that are re-flexed back at maturity. Flowers have 2 male stamens, with a single female two lobed stigma. Flowers are surrounded by a calyx (green buds) of 4 triangular sepals each about 1–2 mm long.

The fruits are ellipsoidal to almost globular, smooth, purple-black when mature, 1.5–2.5 cm long, with an edible flesh surrounding a single stone or seed which is brown to black (Green 1986; Jeanes 1999; Green 2002).

There are many named cultivars of olive, including ‘Barnea’, ‘Kalamata’ and ‘Manzanilla’, (Government of South Australia 2021)

For further information or assistance with the identification of European Olive, contact the herbarium in your state or territory.

Flower colour

White, Cream

Growth form (weed type/habit)

Tree, Shrub

Where it currently grows? Preferred habitat

European Olive grows in areas receiving at least 500 mm rainfall per year, with cool winters and hot, relatively dry summers. It thrives in natural and modified habitats with moderate levels of soil nutrients and grow in a wide range of soils from deep loams to rocky outcrops. It has become naturalised along roadsides, and in bushland, waste areas and disturbed sites (Parsons & Cuthbertson 1992).  European Olive is well-adapted to cool wet winters and warm dry summers, and very tolerant of drought. 

Are there similar species?

European Olive is of very similar appearance to African Olive (Olea europaea subsp. cuspidata). 

African Olive normally has larger leaves; from 6–10 cm long,  and wider leaves 1–2.5 cm wide, with the lower surface green or yellowish brown.  

European Olive normally has smaller leaves; from 3–7 cm long, and thiner leaves 0.8–1 cm wide, with the lower surface whitish or silvery.

Olives can also be confused with some native species, including Australian Olive (O. paniculata), which has relatively small fruits (about 10 mm long, compared to 15-30 mm for European Olive) occurring on the east coast from Newcastle in New South Wales to far north Queensland past Cairns and Port Douglas to Lockhart. 

The Mock Olives (Notelaea spp) also have relatively small fruits, and Boonaree (Alectryon oleifolius) has alternately arranged divided leaves and dry fruits (Navie 2004).

Why Is It A Weed?

What are its impacts?

European Olive has impacts on both environment and agriculture and has become a major environmental weed in parts of temperate to humid south-east of Australia, mainly South Australia and Victoria. Government of South Australia (2021) states that self-sown seedlings establish on roadsides, in bush and abandoned pasture and may be slow-growing at first, with a juvenile period of 5-10 years before they begin to bear fruit. But established olive trees form a dense and permanent canopy that prevents other vegetation from re-establishing. Individual trees live for many centuries and retain the ability to regenerate from stumps after felling or burning, as well as forming a large seedbank in the soil. Olives are very long lived and accumulate a large seedbank. It is estimated that individual olive trees in the Mediterranean region are more than 1500 years old (Government of South Australia 2021). It is widely planted as a commercial crop in Australia and gradually becoming a severe bushland weed. The pollen a known allergen causing hay fever in susceptible individuals. 

Agriculture: In grazing paddocks, the plant may be effectively controlled by stock, as it is quite palatable, but it can become a major weed of parkland where grazing is low or absent.  Olives are highly flammable due to their oil content and therefore increase fire risk compared to grazing or other horticulture Government of South Australia (2021). 

Native ecosystems: Olives are very adept at invading and establishing in new environments to become the dominant plant species and is able to invade most healthy intact native vegetation, including woodlands, grasslands, and is a major pest plant of grassy woodlands and invade riverine environments (Agriculture Victoria 2021). Olives out compete native vegetation reducing both floral and faunal biodiversity, and contain volatile oils increasing bushfire risk. It can alter the composition of native vegetation by shading and crowding out other species and preventing their regeneration (Parsons & Cuthbertson 1992; Muyt 2001). Olive infestations reduce the abundance and diversity of native plant species, altering the canopy structure of woodlands and preventing native regeneration. Native canopy cover may be reduced by 80% and native species diversity by 50% (Government of South Australia 2021). However, the infestations providing a fruit crop rich in fats can be significant for many small bird and mammal species. Species reported eating the fruit and dispersing the seed include many birds including emu, currawong and silvereye, and other animals like wombats (Agriculture Victoria 2021), with seeds spread by animals particularly birds in to new weed free natural areas and other environments.

Urban areas: A weed of roadsides and waste land, parks and urban plantings, and pockets of remnant and re-vegetated native vegetation.

How does it spread?

European Olive spreads mainly via seed and is mainly dispersed by animals, particularly birds, and by soil movement and on machinery. Over short distances, dispersal is via native an introduced birds including European starlings, ravens blackbirds, starlings, ravens, pigeons, magpies and noisy miners. Other animals, such as foxes and wombats that eat the seeds also spread Olives (HerbiGuide 2021; Parsons & Cuthbertson 1992; Navie 2004). Long-distance spread is usually through the nursery trade with ongoing escapees from tree crops and gardens contribute to the wild population.

What is its history in Australia?

Olives were first planted by John Macarthur at Parramatta in 1805, although these may have been African Olives Olea europaea subsp. cuspidata. It has since been widely cultivated in southern Australia (Parsons & Cuthbertson 1992). 

How To Manage It?

Best practice management

European Olives can be controlled by physical means, both with hand tools for smaller plants and mechanically with machinery for larger plants sometimes in conjunction with herbicides as part of integrated controls. In parkland or bushland, control may be achieved by physical, mechanical or chemical means. Effective control requires a long-term plan as trees are hardy, have a vigorous and persistent root systems and a substantial long-lived seed bank, with regrowth and ongoing germination requiring a continued control effort over many years for mature and established populations.

Non-chemical control: European Olive plants are readily controlled on farms by increasing grazing. Smaller seedling to sapling to 30-10 cm tall can be hand pulled when the soil is moist through enabling removal of the large tap root with disturbed soil should be tamped down after removal preventing further germination of olives or other weeds. During drier times or for larger plant to 1.5 metres, may be grubbed out with a mattock or chip-hoe. These and lager trees and established old populations and shrubs can be cut down and treated with chemicals will normally require repeated herbicide treatment to kill the plants.  Drill and fill Holes are drilled 2-3 cm deep, into the lignotuber and trunk, about 40 mm apart and for a minimum of three rows. A registered herbicide is then applied within 20 seconds to the holes.  Frill and fill Grooves are cut with a hatchet or chainsaw around the lignotuber and trunk, 2-3 cm deep, about 40 mm apart (being careful not to ringbark the plant), at a 450 angle and for a minimum of three rows (the more the better). Fill each groove or cut with herbicide within 20 seconds. Suitable for small and mature trees. Can be treated all year, however avoid hot periods when the plant may be stressed. Removing mature trees and populations usually resulting in heavy seedling regeneration so followup work over many years is likely required. Mature trees and their stumps can be bulldozed or mechanically removed, however the potential damage this may cause to soils must be weighed up (Government of South Australia 2016).

Chemical control: For smaller plants to 1.5 metres tall spot spraying is effective with a registered herbicide at label rates, and the Cut and swab method where the trunk is cut as low as possible to the ground and painted (swab) with a registered herbicide within 20 seconds. Mature plants are best controlled by applying herbicides to cut stumps or basal parts of the plant that have been exposed by peeling back the bark. Seedlings and small plants can be treated by herbicide spraying. In all cases, follow-up is important to control resprouting and seedling germination (Parsons & Cuthbertson 1992; Muyt 2001). Direction for controlling Wild Olives (Olea europaea) using the basal bark treatment can be seen at, Government of South Australia (2016). All techniques should be monitored and any regrowth or new seedlings treated via the hand pull, grub, basal or spot spray techniques.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

European Olive is a perennial evergreen plant. Seeds germinate in autumn, and plants grow for several years (5-10) before flowering commences. Flowers are borne in October and November, and fruits ripen in the summer (Parsons & Cuthbertson 1992). 

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

European Olive is widely naturalised in coastal and tableland areas of South Australia, Victoria and New South Wales. It also has a limited distribution in southern Queensland and south-western Western Australia (Parsons & Cuthbertson 1992; AVH 2008; Queensland Herbarium 2008).

Where does it originate?

The geographical origin of European Olive is difficult to determine because it has been widely cultivated for thousands of years, but it is probably native to the Mediterranean area (Green 1986; Parsons & Cuthbertson 1992).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

SA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Olea europaea subsp. europaea

Other scientific names (synonyms)?

Olea europaea L.

Does it have other known common name(s)?

European Olive, Olive, Wild Olive.