Natural regeneration experiment

In less than three years since it was completely cleared of vegetation, a section of Enoggera Creek bank at Walton Bridge Reserve has been entirely revegetated by natural recruitment.

Upstream from the footbridge where Enoggera Creek meets Fish Creek, the section of creek bank is about 20 metres long and 10 metres wide.

In the month of February 2022 Walton Bridge received 1023 mm of rain – most of it in the last week of the month. In the flooding, two huge River Oak Casuarina cunninghamiana on the other side of the creek bank fell over crashing into an ancient Weeping Lilly Pilly Waterhousea floribunda* taking out most of its branches. Those trees crashed into the footbridge and the force of floodwaters coming downstream brought more fallen trees creating a huge pile of debris on the footbridge.

That footbridge connects The Gap bikeways to the rest of the Brisbane network. In the days that followed, the Brisbane City Council infrastructure crews got to work to clean up. The only vegetation which remained after they were done was the Waterhousea stump about 1.5 metres high and a few battered Creek Matrush Lomandra hystrix.

For the local park users, Walton Bridge bushcare volunteers led by Anne Jones and our Habitat Brisbane officer Jodi Rees, it was totally devastating.

It was fortunate that the bushcare group didn’t start replanting immediately because a few months later Enoggera Creek flooded again.

Later that year, Anne and Jodi walked the site discussing how to proceed. There was already evidence of regrowth – plenty of weeds but lots native plants too. Then Jodi said, “Why don’t we just let it grow and see what happens?”

And so we did. While there has been some weeding in the area, it’s been a light touch. Mostly the emphasis has been on removing weedy grasses like Green panic Megathyrsus maximus var. maximus and vines especially Balloon Vine Cardiospermum grandiflorum and Glycine Neonotonia wighii. Also the usual weedy trees Camphor Laurel Cinnamomum camphora, Chinese Elm Celtis sinensis, Wild Tobacco Solanum mauritianum and Devil’s Fig Solanum chrysotrichum.

The most exciting part is to see what grew. For a start the old Waterhousea has tripled in height. There have been many pioneer plants popping up such as Acacia sp., Native Rosella Hibiscus heterophyllus, Poison Peach Trema tomentosa and Macaranga Macaranga tanarius.  A nearby Black Bean Castenospermum australe has dropped loads of beans which have sprouted up. Masses of Lomandra hystrix and Waterhousea are growing fast.

Other plants interesting include River Lily Crinum pedunculatum, Native Willow Primrose Ludwigia octovalvis, Large-fruited Raspberry Rubus probus in profusion, and various Cyperus sp., Eucalyptus sp., Persicaria sp. and so on.

Thanks to everyone who’s contributed to this experiment in natural recruitment including Habitat Brisbane, Brisbane Bushcare, Queensland Herbarium, Janet Mangan and our dedicated volunteer bushcarers.

* The photo of the mature tree which appears at this link Weeping Lilly Pilly Waterhousea floribunda is a “before” photo of the tree reduced to a stump in 2022.

The site in November 2022. Photo: Anne Jones

22 November 2024. Photo: Anne Jones