After successful control of Japanese knotweed we need to pre-emptively tackle the risks of re-invasion from secondary invasive plant species. Across habitats in the UK, Himalayan balsam is one of the most prolific and potentially damaging of these invaders.
Himalayan balsam is one of the fastest plants to invade empty habitat niches
Whilst the focus of many invasive non-native control programmes is oriented to the multi-year treatment of Japanese knotweed, the empty niches created following successful treatment leave this habitat open to re-invasion by species such as Himalayan balsam. Balsam in it's own right presents a costly and serious threat, particularly along waterways and riverbanks.
Himalayan balsam spreads aggressively thanks to its substantial production of seeds and ballistic seed rain - individual plants can have scores of these unusual seed pods, which literally explode upon physical contact late in the season, scattering seeds up to 7 metres away.
A stand of Himalayan balsam can have up to 6000 viable seeds
Secondary invasion from Himalayan Balsam creates a host of ecological and practical issues for land managers. Balsam invasion can:
- Reduce amenity value by obstructing waterways
- Damage riverbanks and degrade freshwater quality
- Encourage major soil erosion
- Impact on biodiverse habitats and fish spawning beds
By integrating secondary invasion treatment into the initial vegetation management strategy we reduce future treatment and control costs and maximise value throughout the treatment lifecycle.
Understanding habitat dynamics allows us to maximise the return on initial treatment costs for primary invasive plants
We're going into the third year of our research programme into the effective control of Himalayan balsam. The research team, led by Dr Gareth Bruce and our in-house Environmental Scientist Iván Martín-Domínguez, are already using the early outcomes of the work to advise on a more complete vegetation management toolkit centred on Japanese knotweed treatment.
Full outcomes of the research are expected for 2022.