Pest plant - Olives

  • Fact sheet
  • August 2015
olive-seedling
Olive seedlings

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.

Description

  • 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.

Distribution

  • 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.

Ecology

  • 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.

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