The olive tree (Olea europaea) was introduced from the Mediterranean area as a tree crop. It is now established in many parts of South Australia, causing a major problem in native vegetation.
- erect, bushy evergreen tree to 12m, with a deep, widely-branched, woody root system
- trunk branches from the base and has rough black bark
- leaves are 3-8cm x 1-4cm, narrow and tapering to a point, glossy dark green on top, silvery below
- in late spring, tiny cream flowers in large clusters with four petals and four protruding stamens
- fruit is ellipsoid, 1.5-3cm long, purple-black when fully ripe
- each fruit contains one brown oblong seed, 1.5cm long
- seedlings have smaller oblong leaves, arranged rigidly in opposite pairs.
Why is it a problem?
- invades native vegetation, especially in dry sclerophyll forest or woodland and adjoining cleared, ungrazed land
- can alter the composition of native vegetation and decrease biodiversity
- fire hazard.
- Eyre Peninsula – isolated infestations but high risk of spread to native vegetation
- Northern pastoral – common in southern Flinders Ranges, isolated plants elsewhere
- Northern agricultural districts and Yorke Peninsula - common on roadsides and native vegetation in the higher rain fall areas
- Murray Mallee - isolated outbreaks along the Murray River and in irrigated areas
- South East - isolated plants on roadsides and some reserves
- Central region - common in the Mt Lofty Ranges.
- grows well in most environments, particularly where winter rainfall is high and summers dry
- grows on a wide range of soil types but will not survive in waterlogged soil
- highly inflammable due to their oil content and can regenerate from stumps after fire
- seeds germinate mainly in autumn and seedlings grow during winter
- flowering does not begin for several years appearing in October and November
- fruit develops slowly over summer, the ripe fruits hanging on the tree for a long period during the following winter.
How it spreads
- birds and foxes eating the fruit and dropping the seeds elsewhere
- development of commercial olive orchards has increased spread throughout South Australia
- seed may be moved locally in soil during earthworks.