Himalayan balsam (Impatiens glandulifera) is an annual plant that reproduces only by seed. It originated in the Himalayan mountains and is a well-known invasive plant along riparian areas across Europe, Asia, North America and New Zealand.
This weed grows extremely tall and fast, reaching up to 3m in height by the end of the season. Stems are erect, purplish and easily broken.
Leaves are lance-shaped and 6-15cm long, borne oppositely or in whorls. Leaf size decreases with height on the stem.
Flowers and Fruit
Himalayan balsam has large (2.5-4 cm long) pink flowers. The upper petal forms a hood overtop of the reproductive structures, while the lower petals form a landing platform for insect pollinators. At maturity, the seed capsules explode, flinging seed as far as 5m from the parent plant. One plant may produce up to 800 seeds that remain viable when fully submerged underwater for up to two years.
Himalayan balsam requires moisture to flourish, hence its preference for riparian areas and waterways. As an annual, it depends on disturbed soils (caused by flooding, development or erosion) to quickly establish and shade out all competing vegetation. It is sensitive to frost and drought and adapted to grow at high elevations - up to 4000m.
This invasive plant is devastating to sensitive riparian habitats, shading out native vegetation and leaving soils exposed and susceptible to erosion when it dies in the fall. Its high nectar content and long flowering season draw pollinators away from native plants.
Never purchase or grow Himalayan balsam. It may be sold under several common names, including:
- Poor Man's Orchid
- Policeman's Helmet
- Indian Balsam
- Ornamental Jewelweed
After establishment, seeds spread with riparian soil movement and will colonize any disturbed soil, so always ensure adequate competing vegetation is present to ward off infestations. Always complete control operations before flowering to prevent seedset.
Hand-pulling is by far the most effective control method, as Himalayan balsam has a shallow root system and often grows in areas that cannot be cultivated or mown. Bag the plants and take them to the landfill for burial.
Both glyphosate and 2,4-D have shown efficacy against this plant; however, regulations on spraying near water must be followed. Plants in flower can still produce viable seed after being sprayed.
This plant is designated as Prohibited Noxious in Alberta, which means that under the Weed Control Act, it must be completely eradicated wherever it is found.