The Southern Otway Landcare Network (SOLN), along with its partner organisations, has decided to prioritise emerging weeds. By implementing targeted and comprehensive control, we hope to be able to remove new weed species before they become widespread. This benefits the environment, is an efficient use of resources and provides some positive results for our members.

Along the eastern branch of the Barham River tree dahlia (Dahlia imperialis) has escaped from gardens and is rapidly spreading along the course of the river. Tree dahlia is a fast growing perennial from South America. It grows up to five metres high with thick bamboo-like canes and has large purple flowers. Tree dahlia grows quickly in riparian areas, choking out native species and altering the hydrology and natural ecosystem of the river.

Late last year, while cycling home after work, I got chatting with a local landholder who was concerned about the spread of weeds. According to Greg Ware, the tree dahlia had spread more than a kilometre in the past five years. I suggested a monthly working bee and Greg jumped at the idea.

Our first working bee, in conjunction with the Otway Barham Landcare Group (OBLG), was on Greg’s property on the Barham River near Apollo Bay, where we trialled cutting the tree dahlia, pasting the cut ends with herbicide, and stacking the branches on a large blackberry patch. Removing the branches was critical as tree dahlias send down roots and re-sprout from fallen branches. Recent heavy rains meant the river had swollen so we were not able to access as many of the clumps as we had hoped, but we removed three infestations on the near bank and got the ball rolling.