Most Unwanted: Himalayan balsam
Impatiens glandulifera
Habitat: Terrestrial
Threat: Threatens river bank habitats and species
Status: Established
This species is very common throughout Ireland. It has been spread as a garden plant and is now colonising and becoming locally abundant along riverbanks to the detriment of native species of flora and fauna.
What is it?
This garden escapee is quite an attractive plant and is found colonising riverbanks and areas of damp ground. In these locations it can form dense monospecific stands where individual plants can reach 2 – 3 m in height (one of the tallest annual plants in Ireland). The stem of the plant is smooth, hairless and hollow. They grow upright, easily broken and are usually purple in colour with many large oval-shaped pointed leaves bearing teeth around the edges. The flowers of this plant can vary in colour but are usually shades of white, pink or purple. Flowering usually takes place from June to October. Seed capsules arise where the flowers were and when mature and dry, the slightest touch causes these fruits to split open explosively dispersing seeds up to 20 feet from the parent plant. Seeds are capable of further dispersal by water and animal and human aid. Each plant can produce a high number of seeds, which can remain viable upwards on 18 months. Seeds are not frost hardy.
Impact
This species grows in thick monospecific stands, shading out native plants such as grasses. From October onwards, the plants die back leaving the soil more exposed to erosion because of the loss of native plants earlier in the year. It has also been shown to produce more nectar in its flowers than native species making the plant more attractive to bumblebees resulting in less pollination of our native species.
Where is it from?
The plant is native to the western Himalayas but is now invasive in many parts of continental Europe. In Britain, Himalayan balsam is regarded as one of the top-ten most wanted species that have caused significant environmental impact.
Where are they in Ireland?
The species is now found throughout the island of Ireland suitable habitats.
How did it get here?
Originally brought into Ireland as a garden plant.
How are they spreading in Ireland
Escape from gardens.
Natural dispersal.
Contaminant of soil
What you can do
Do not plant this species in your garden.
Report all sightings.
Download the Best Practice Management Document for this species.
Additional reading
Habitas Invasive Alien Species in Northern Ireland
