Botanic Gardens Trust, Sydney, Australia

Australian Botanic Garden

African Olive update April 2012

Endeavour Energy African Olive control program

The African Olive control program is now in the third year of implementation and saw a continued focus on controlling olive infestations in areas of good native tree canopy, combined with larger scale mechanical clearing of dense olive areas along the Eastern Ridge and Mount Annan areas.

  • Mechanical clearing of dense olive infestation - A total of 2.5 hectares of mechanical clearing and chipping of olive was completed by local contractor Brad Parrish in the steep hills north of the Kurrajong track, which is an extension of the regeneration work completed in the adjacent series of gullies. Olive stumps were ground down to soil level and treated with Garlon/diesel herbicide mix. All native trees were conserved and some sections of olive were retained for habitat purposes. February 2011, Contractor: Parrish & Son Pty Ltd.
  • Basal bark spray technique for olive control - A new herbicide control permit has been issued for African Olive control, which allows for a higher rate Garlon/diesel to applied as a basal bark spray. Contractor Greening Australia has been using this technique to control large stands of African Olive. Areas treated include large isolated olives near high value woodland conservation areas. Area treated: 2 hectares. January 2011, Contractor: Greening Australia.
  • Olive control in wooded gully - northern sector - Primary olive control was completed in this 3.5 hectare gully area located in the north east sector of the estate. This gully has very high regeneration potential due to the well developed extant canopy of native eucalypts. Large olive trees invading the understorey were treated by drill and injection of herbicide. January-February 2011, Contractor: Ecohort Pty Ltd.
  • Direct seeding using hydromulch technique - A 1.2 hectare area was treated with a native grass/tree/shrub seed mixture to assist natural regeneration of previously cleared olive areas. Areas targeted included gully areas prone to erosion. A key focus will be the continued refinement of these direct seeding techniques to accelerate the regeneration of native species. Contractor: Cumberland Plain Seeds.
  • Tree planting for screening of powerpoles and regeneration of cleared olive areas -
    1500 local species trees were planted across the site as part of the original powerline construction agreement with Endeavour Energy. Trees were propagated at the ABG nursery and planted out and maintained by Endeavour Energy contractor T & J Landscapes in accordance with the Visual Assessment Study.  These trees will eventually provide screening of new powerpoles from key vantage points with the Garden. An additional 500 trees were planted at several cleared olive sites to replace trees removed during powerline construction and assist with regeneration of the tree canopy. All trees have responded well to favourable rains throughout this current summer. June-September 2011. Funded by Endeavour Energy.
  • Mechanical clearing of dense olive infestation - Eastern Ridge - Work continued on controlling the large dense olive infestations along the Eastern Ridge during October 2011 through to March 2012. With approximately 58 hectares of dense olive remaining on the Eastern Ridge and Mount Annan summit areas, a contract for 20 hectares of mechanical clearing/mulching was awarded to contractor Parrish & Son Pty Ltd. The contract identified 8 individual sites to be done as a ‘mosaic’ to ensure retention of vegetation for fauna habitat. Within each clearing site small ‘islands’ of olive are also retained for interim habitat and soil stability along drainage lines until native plants establish. Clearing works in the southern portion of the Eastern Ridge have opened up views of the historic water canal aquaduct. This location has excellent potential as a new visitor walk and interpretation point for the water canal and aquaduct. October 2011 - April 2012. Contractor: Parrish & Son Pty Ltd.
  • Power pole decommissioning  - Endeavour Energy completed the decommissioning of the first set of 66kv timber poles in the northern and central sectors of the Garden. One set of these timber ‘H’ poles remains in the southern sector of the garden along Caley Drive. Construction of the new 132 kv line has proceeded during December 2011 - March 2012, with a section of this line now located near the Banksia Garden.
  • Research program - A research program on African Olive ecology and restoration techniques, in conjunction with Macquarie University - Plant Invasion & Restoration Ecology Lab, has been continuing since 2006. The fourth research paper by Peter Cuneo and Michelle Leishman ‘Ecological impacts of invasive African Olive in Cumberland Plain Woodland, Sydney, Australia’ has recently been accepted for publication by the ecology journal Austral Ecology. A further research paper on ecological restoration following African Olive invasion is in preparation and is expected to be published later this year.

Peter Cuneo
Manager - Natural Heritage
24 April 2012 





Mechanical clearing contract areas 2011-2012





Powerpole screen plantings in Eastern Valley

Historic water canal aquaduct now visible after dense olive clearing

Clearing along Eastern Ridge with ridgeline Bunya Pines now prominent