Himalayan balsam

An annual, hairless herb with pink, white, or purple flowers and an erect, thick-branched main stem which is less than 2.5m tall. It dominates native species and competes with them for light and space.

Description

• Main stem is fleshy, hollow, ribbed, and has purple-reddish junctions of the leaves and branches.
• Leaves have sharply serrated edges and taper to a fine point.
• Its pink, white or purple flowers from November to March are held on stalks less than 37mm long.
• Hairless, ribbed seed capsules (2-3cm long) are usually purplish on the exposed side and open when disturbed, explosively releasing shiny black seeds (3.5-5mm long).
• Reproduction is by seed only. Seeds float and are spread by water movement.
• Habitats include river edges, riparian areas, gullies, wetlands, forest margins, roadsides, and ditches.
• Prefers moist soil and full sun to light shade.

What you need to know

Competes with native plants for light, space and pollinators. It can dominate the vegetation on stream banks, leaving them bare over winter and prone to erosion.

Management approach

Community Led

These organisms have not been legally declared as pests but may be of interest to the public as they occur regularly in the environment. They may be capable of causing adverse effects to the values of Waitaha/Canterbury.

Consider removing this invasive species from your property and consult your local council for appropriate disposal. Consider lower-risk alternatives for your garden, such as native plants.

Control

Physical control

Hand-pull seedlings and small patches before seeding (spring to summer).

Cut stems (spring to summer): cut close to the soil below the first node (leaf joint) before seeding.

Plant parts for disposal: seeds.

Contact your local council for appropriate disposal locations.

Chemical control

Overall spray (full leaf): glyphosate (10ml/L + penetrant) or metsulfuron-methyl 600g/kg (4g/15L).

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Biological control

Biological control is currently not available for this species.