Himalayan Balsam(Impatiens glandulifera)
Himalayan balsam is an invasive terrestrial species that was first introduced in 1839 as an ornamental garden plant. Since it was introduced, it has spread to most parts of Ireland. In its home range, the Himalayas, it has adapted to develop thousands of seeds due to the nutrient poor soil and cold temperatures. Unfortunately due to our warmer climate and nutrient rich soils it has thrived here and became highly invasive.
- Perennial plant which can reach between 4-7 ft in height.
- It has a hollow stem which, nearer the base of the plant, can often have red roots extending from the stem down towards the ground.
- Dark green leaves, lance-shaped leaves with serrated edges.
- It generally colonize river banks as the seeds are easily distributed by water but can be found in a range of other environments.
- The plant can produce little pink flowers throughout the growing season. Each plant has the potential to release up to 2,500 seeds.
- These are in the form of hanging seed pods, that when disturbed can throw seeds over 6 metres away from the original plant.
- Due to the nature of this, it is often spread by human and animal activity, when brushing up against the plant. e.g walkers, livestock.
- Cutting: Cut at ground level (the plant must be cut below the lowest node to stop regeneration) using a scythe, flail or strimmer before the flowering stage in June. Cutting earlier than this will promote greater seed production from plants that regrow. Cutting should be repeated annually until no more growth occurs.
- Pulling: Shallow-rooted plants can be pulled up very easily.
- Biological: Grazing by cattle and sheep is effective from April throughout the growing season in some situations. It should be continued until no new growth occurs. Grazing on riverbank habitats can however have negative impacts such as poaching of river banks and the removal of other native vegetation which may act as a buffer zone.
- Chemical treatment by herbicide can be achieved with a weed wiper in mixed stands, or by foliar spray in dense stands.