This plant was introduced to the UK in 1839 from Northern India. Himalayan or Indian Balsam is most commonly found on riverbanks and damp areas, though it is capable of thriving in many other habitats.
Due to a lack of natural predators and diseases this invasive plant spreads rapidly. It forms dense clumps which can grow up to 3 metres tall and dominate an area. These shade out our native plant species which prevents their growth. In late autumn the plants die back leaving the area bare of vegetation and vulnerable to erosion.
Himalayan Balsam also causes a less obvious problem for native species. Like many flowering plants, Himalayan Balsam produces a sugary nectar to attract insects. However the flowers produce more nectar than any other native European species. This makes it more attractive to bees and other insects, luring them away from pollinating our native flowers.
Stages of growth
Seedlings
The seedlings of this annual plant begin to emerge as early as March.
Leaves
The leaves are dark green and lanceshaped. They have a dark-red midrib, serrated edges and can grow up to 150mm long. The stems are pinkish-red, brittle and hollow with side branches originating from joints in the stem.
Flowers
Himalayan Balsam can grow up to 3 metres tall. Characteristic slipper shaped purplish-pink or white flowers beginning to appear in June.
Seed pods
In late July/August its distinctive 'exploding' seed pods mature which are capable of catapulting its white, brown and black seeds distances of up to 7m. Each pod can contain up to 16 seeds.
Control must be carried out before seed pods mature
- Cornish trials have shown that Himalayan Balsam seeds only remain viable in the soil for 1 year. Therefore, if effective control is carried out before seeding, complete eradication can be achieved in one season.
- Strimming or cutting is an effective control. Ensure all stems are completely severed below the lowest node or joint.
- Pulling or uprooting is also a very effective control. However, as some seedlings can mature as late as November, the site must be closely monitored and any late emerging plants pulled.
- Care must be taken to completely uproot each plant. Plants with broken or damaged stems which are still rooted are able to continue growing and seeding. Cut or pulled plants can be safely left on site to decompose, though this must be done in a dry open area.