Free a Tree

Friends of Black Hill and Morialta Inc.
For payment by card. (Other payment options are available)


What is the 'Free a Tree' project?

The Free a Tree project was created to bring community attention to the plight of significant eucalyptus trees in the Black Hill Conservation Park.

In 2017 volunteers realised that significant eucalyptus trees in the Black Hill Conservation Park's Ambers Gully grassy woodland site were dying due to the extra pressure put on them when their base becomes surrounded by wild olive trees.

The project has two main aims:

  1. To protect the existing significant trees by killing the olives which surround the trees showing the greatest signs of stress. Literally, it is freeing a tree today so it is still alive tomorrow!
  2. To remove the olives scattered throughout the site which will reduce the seed source causing the problem and protect the biodiversity of the grassy woodland in the long term.

Tree health comparison.

Current Status

After initial analysis and trials were completed a fundraising initiative partnering the Friends of Black Hill and Morialta with Landcare Australia ran from June - August 2019 allowing the acceptance of tax deductible donations. This campaign run through the Landcare Australia website raised $7545.00 from 68 donors.

These funds have been used to save the most stressed eucalyptus trees in the Ambers Gully project site, however the project continues to run to monitor for seedling olive emergence and to reduce the overall spread of olive within the Ambers Gully site.

In time the intention is to extend the project through the Sugar Loaf area of the park which also has similarly stressed eucalypts and into our Ghost Tree Gully project site which has already had significant olive removal work performed by volunteers.

In November 2019 the Friends of Black Hill & Morialta Gift Fund became a gift fund listed on the Register of Environmental Organisations under item 6.1.1 of subsection 30-55(1) of the Australian Income Tax Assessment Act 1997 (Cth). Donations of $2 or more are placed in the Friends of Black Hill & Morialta Gift Fund and are tax deductible in Australia. You can now make a donation directly to the Gift Fund.

Same tree 13 December 2019 v 10 July 2020

How do the olives affect significant trees?

Significant trees at this site are a victim of their own success. As they grow in a grassy woodland environment they have the space to produce long horizontal branches which woodland birds love to perch on. The trees spread much further and wider in a grassy woodland than they do in a more closed forest environment where the trees grow tall and close together, with no room or light for branches to spread out. This is problematic as the same birds may have visited the nearby olive trees and eaten the fruit, sitting along the full length of the extra wide branches they then deposit beautifully fertilised olive seeds all around the base of the tree.

Over time the small olive seedlings become larger olive trees, which then compete with each other and the eucalyptus tree they are growing under for both water and nutrients. Over time the eucalypts become visibly stressed, losing leaf cover. Ultimately the olive trees win the battle for survival as they have no local natural predators.

Grassy woodland.

Why is this a concern?

If the number of stressed and dying trees was small and the number of olives manageable then we would not be so concerned, however we are noticing that a large number of significant trees in the area are affected and there is a very real concern that a particularly dry summer could tip a large number of trees over the edge all at once. This would lead to too many large trees dying, too much loss of habitat and could possibly lead to wholesale collapse of this grassy woodland ecosystem.

Kennedia prostrata

Why are grassy woodland sites important?

Remaining native grassy woodlands are important here in South Australian as many original woodlands were utilised for grazing purposes by settlers and have now been lost. As well as large imposing trees in the overstory they have a minimal mid-layer of vegetation and a significant diversity of species in the understory. This includes all manner of plants such as lilies, ferns, daisies, orchids and many other different species of herbaceous plant. As the name suggests they also contain a vast array of native grasses.

The greater the variety of the flora, the greater the variety of insects the woodland can support. Butterflies, bees, bristleflies and bugs all help to make up a wide and varied diet for our native fauna. This vast array of insect life is vital for the survival of our woodland birds. We know from the Biodiversity report submitted to SA parliament 2017 that many woodland bird species regarded as common thirty years ago have now disappeared altogether from a number of areas in the Mount Lofty Ranges and are in serious decline all over the state.

Small woodland birds need large trees with spreading horizontal branches to perch on when searching for food on the ground. Grassy woodland site provide this.

Grassy woodlands are in decline generally across South Australia and this particular grassy woodland site contains a number of regionally threatened ecological communities including Drooping Sheoak, Black Mallee Box, Blue Gum and Red Gums.

Meadow Argus butterfly

Superb fairy-wrens.

What is a significant tree?

For us a significant tree is any tree which has reached an age where it has viable nesting hollows. In the case of blue gums and red gums a small hollow with narrow entrances suitable for small mammals (such as antechinus) to inhabit take about 100 years to form. Hollows of a medium size which would be suitable for parrots to nest in take around 200 years to form, and the larger and deeper hollows occupied by bigger birds such as cockatoos and owls can take much longer.

Yellow-tailed Black Cockatoo.

Why are significant trees important?

Significant trees are important as they contain nesting hollows. Every single Australian parrot species requires a nesting hollow to breed. So every single parrot pair needs a two hundred year old tree in order to nest naturally in Ambers Gully, for larger species like the vulnerable yellow tailed black cockatoo which nests in the area that age is even greater as they are a much larger bird.

Many other native bird species like the white-throated tree creeper, the owlet nightjar and the nankeen kestral all use hollows for nesting as do a number of mammals, in particular bats, antechinus and possums.

Yellow-footed Antechinus

Is Ambers Gully that important?

As well as providing habitat for a huge variety of native plants which in turn support insects, woodland birds and small mammals the Ambers Gully site is an important nesting site for a number of raptors. Tawny Frog mouths, Collared sparrowhawk and Brown goshawk were all photographed nesting and successfully fledging young in the project site in the summer of 2017/18.

Wedge Tailed eagles have also been observed roosting in the larger trees and Square tailed kites have been observed flying over the site.

The site is also home to koalas, kangaroos, possums, echidnas, frogs and reptiles which are all precious native animals.

Tawny Frogmouth

What has been done so far?

Once we had an understanding of the underlying issue we mapped the site to determine where the areas which most needed our attention were. We also determined which trees were showing the worst signs of stress.

We have held Fund Raising BBQs and utilised donations to employ contractors on the steeper, less accessible areas of the site not suitable for volunteers. Yes, we have already freed a number of trees!

Volunteers have removed scattered olive in some higher quality bush areas with help from the 4WD Adventures club who provided transport and workers.

Contractors have treated olives surrounding the most severely affected significant trees in the Ambers Gully site.

Olives around a stressed gum tree.

How can I help?

Donate to the Friends of Black Hill & Morialta Gift Fund. All donations over $2 are tax deductable. If you particularly wish your donation to be spent on this project please let us know when supplying your contact details.

Spread the word about this campaign! The more people who help out in any way they can the greater impact we can have.

Volunteer your time. The Friends of Black Hill & Morialta in conjunction with the 4WD Adventurers club hold habitat restoration events at the site each year. See our events page for more details of upcoming events.

Join the Friends group and become a long term supporter of our conservation parks. Many of our supporters are not volunteers on the ground, but we value each and every membership as every one helps support the work we do in parks.

Out on a limb - there may soon be no return.

What will my money buy?

You can donate to this project by donating to the Friends of Black Hill & Morialta Gift Fund and advising us when providing your contact details you would like the funds to be used on the Free A Tree project.

Treated olives.

Friends of Black Hill and Morialta Inc.
For payment by card. (Other payment options are available)


Thanks to Danny McCreadie for the use of his photos.


27 Jul 2020 - Page Updated - Project update.

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