Botanic Gardens Trust, Sydney, Australia


African Olive control program


African Olive (Olea europaea ssp. cuspidata)  is a medium-sized dense crowned tree with a small black fruit. The main centre of natural distribution for African Olive is eastern Africa, where it occurs from the desert shores of the Red Sea to the high rainfall mountain regions of Uganda. African Olive was introduced into Australia as a hedging plant and rootstock for the edible common olive (Olea europaea ssp. europaea) in the early 1800s.

The Camden region in south-western Sydney is an early Australian introduction site for African Olive, which has asserted itself in recent decades as an aggressive woody weed. African Olive is well established as a serious weed in the subtropical climate of Norfolk Island and Hawaii and in 1992 occupied 6000 ha of the Hawaiian Volcanoes National Park.  African Olive is a very long lived tree (100 years+) and seed is spread by birds who consume the small black fruits.

African Olive is listed as noxious weed in NSW and South Australia, and is listed nationally as a potential environmental weed. Current extent of spread in south-western Sydney and extension into the Hunter Valley suggests a potential for spread well beyond current distribution in NSW. African Olive has led to a decline in native plant diversity, through the formation of a dense and permanent mid-canopy in a wide range of vegetation types in south-western Sydney (Cuneo & Leishman 2006).

Current situation at Mount Annan Botanic Garden

Mount Annan Botanic Garden is a 416 hectare site located near Campbelltown, NSW. The Garden is a unique combination of developed horticultural theme gardens, woodlands and grasslands. With the Garden now surrounded by urban development, the native vegetation remnants have assumed greater significance and are providing valuable refuge for displaced fauna. The native vegetation at Mount Annan Botanic Garden has regionally significant conservation value, and includes the following endangered ecological communities listed under the State and Federal legislation:

  • Cumberland Plain Woodland (reclassified since January 2010 as critically endangered)
  • Western Sydney Dry Rainforest
  • Sydney Coastal River Flat Forest

This endangered bushland is under direct threat from African Olive invasion. The Botanic Gardens Trust has implemented a strategic approach to African Olive control over the past 10 years, which has focused on olive control in the highest quality bushland areas.

Large scale African Olive control across the estate is currently beyond staff resources, with the current level of African Olive infestation estimated to be:

  • 75 hectares of dense African Olive forest
  • 31 hectares of woodland invaded by African Olive understorey
  • 37 hectares of good quality bushland free of African Olive

Integral Energy powerline reconfiguration at Mount Annan Botanic Garden

In order to meet the future energy requirements of planned new residential release areas in south-western Sydney, Integral Energy is required to connect two new 66 kv lines to a new Transgrid substation located to the south of Mount Annan Botanic Garden. This will require the construction of a new set of powerlines within the Garden, and the removal of the current 66 kv timber ‘H’ poles that run across the northern and southern sector of the Garden. Agreement has been reached between Integral Energy and the Botanic Gardens Trust to allow the construction of a new dual 66 kv line along the eastern boundary of Mount Annan Botanic Garden. Construction of these new 66 kv lines commenced late 2009 and work on the eastern boundary is almost complete. As part of this program and ongoing environmental commitment, Integral Energy has agreed to make a significant contribution to the conservation work at Mount Annan Botanic Garden through an allocation of $850,000 towards an African Olive control program. 

Integral Energy African Olive control program - environmental benefits

This large scale African Olive control will be staged over five years and provide the following:

  • Ensure the conservation of high quality endangered bushland that already exists.
  • Reinforce and define native vegetation linkages/fauna corridors across the estate and beyond to the Nepean River.
  • Substantially reduce the amount of mature African Olive trees at MABG to a manageable level, reducing the amount of seed being spread into the surrounding district.
  • Program will include and ecological research and experimental control techniques, and demonstrate best practice in ecological restoration following African Olive removal.
  • Use both natural regeneration, direct seeding and tubestock planting to assist in the re-establishment of endangered bushland.
  • Community information and interpretation of the olive control program through signage and the Botanic Gardens Trust website.

This program is sponsored by