Invasive non-native plants

About the project

Our five target invasive non-native plant species commonly grow alongside riverbanks, burns and watercourses in Scotland. These plants produce large numbers of seeds every year, which are spread by humans, by wind and by water, or have stubborn rhizomes (roots). Seeds or plant/root fragments spreading down the river is a frequent problem and new populations of plants are often found downstream of original growing sites.

To be effective, plant control needs to work at a catchment scale (the main river and all the tributaries and burns that feed into it) so all the plants are removed and there is nothing left to re-infest downstream locations. However, this can be challenging as, in addition to the technical challenges of plant control, it requires multiple landowners to work together to ensure plants are consistently cleared from all river sections. Working with local river and fishery trusts and boards, volunteers and land managers, we are co-ordinating action and undertaking significant control work to reduce invasive plant populations into a maintenance state and move towards eradication.

Monitoring

Every year we undertake monitoring work – surveying sites before treatment to record density (using the DAFOR abundance scale) and re-surveying sites after work has been undertaken to see how successful control work has been and identify priority sites for the next year.

By recording density pre-treatment, we are able to assess progress between years and ensure the site is moving towards eradication. Once a site has been cleared, monitoring continues to ensure the plant does not return from dormant roots or seeds remaining in the soil.

Who is involved?

Consistent annual control is required for a number of years to eradicate an invasive plant from a site. This is why our project trains land managers, local communities, groups and volunteers in pesticide application and best practice in removing target species. By working together we can work towards eradication both at individual sites and across each river catchment.

In cases where invasive plants growing at ‘dominant’ and ‘abundant’ densities (defined using the DAFOR scale) or where access is deemed difficult, treatment is sometimes carried out by professional contractors as well as our project staff and volunteers.

Once infestations are reduced in size and density and control is more manageable, we aim, where we can, to transfer ongoing control to land managers or local groups and communities. In this way, we are able to move our own control effort downstream, working towards ‘source to sea’ control and eradication on a catchment by catchment basis and landscape scale.