Himalayan balsam is one of the top 3 invasive plant species that we work on in the Tees catchment, along with Japanese knotweed and Giant hogweed. Himalayan balsam is an issue across the UK, one of the problems being that it seems to be everywhere! The usual pulling methods can be great for small patches, but working on large monocultures can be time consuming and need to be done consistently to have an impact.
Why is Himalayan balsam so hard to remove?
Root, pull, reroot... Unlike many plants that die when you pull them out, Himalayan balsam is very clever, which contributes to the plant being so successful! If the plant is pulled out, the stems need snapping below the first node. If this is not done, the plant is able to root itself again into the ground from another node in the stem! The plant can do this even if accidentally stood on or blown over by heavy winds! It can also root in several different habitats from woodlands to grasslands.
Exploding seeds! Not only can each Himalayan balsam plant produce up to 800 seeds... they also explode, travelling 5-7m! Especially when Himalayan balsam grows around watercourses, mixed with wind can make the plant spread very quickly! The seeds can also remain viable in the soil for up to 2 years.
Accessibility and reporting - Similar to a lot of other invasive species, Himalayan balsam doesn't always make it easy for us to access and remove them. Especially growing in places that are hard to reach can cause problems when trying to get rid of them. Reporting Himalayan balsam can help us to identify where we need to prioritise and help with planning control.
What are we doing about it?
Biological Control - one of our main projects for our invasive species team is working on biological control. This management process will never fully eradicate Himalayan balsam, but the aim will be to reduce the density of the stands, reduce seed production and allow native species to re-establish. Essentially making this invasive species, no longer invasive. For more information on our biocontrol work, check out our website.
Hand pulling - Biocontrol is still fairly new as a management technique, it is an expensive process that needs a large amount of funding to do. It is also a long process which can take 5 years for a site to fully establish and start spreading! On top of this, Himalayan balsam has been introduced to the UK several times, meaning there are actually at least 3 different strains. Unfortunately, there is not yet biocontrol agents for every strain, so for the sites that are not viable for the rust fungus we try to hand pull the balsam out! We have held volunteer days hand pulling the Himalayan balsam over the past few years, but this is something we would like to do more of in the future.
We do not usually use chemical to spray the Himalayan balsam, due to the volume of balsam around, it would not be practical or beneficial to use chemical spraying. We only tend to use chemicals for eradication of giant hogweed.
Success...
It is a bit early days for us in the world of biocontrol, but so far it has been promising in the results. All of our biocontrol sites have shown signs of overwintering from the 2019 and 2021 releases. Our hope for the future is to have more biocontrol sites along the river, for these to spread and establish. This will hopefully result in the reestablishment of native species, improve soil quality and reduce the impact of erosion and flooding on our river banks.