Balsaminaceae (balsam) family
Also known as
Indian balsam, ornamental jewelweed, policeman’s helmet, Impatiens roylei
Where is it originally from?
Himalayas (Northern Pakistan, Kashmir, India)
What does it look like?
Annual, hairless herb with erect, thick branched main stem (to 2.5 m tall) that is fleshy, hollow, ribbed, purple to reddish tinged and swollen at the junctions of leaves and branches. Leaves (10-20 cm long and 3-8 cm wide) with sharply serrated edges and depressed leaf veins above and raised below, taper to a fine point and have long, narrowly winged stalks (about 8 cm) that are pink above and scattered with purplish glands. Pink, white or purple flowers (November to March) are held on stalks growing near the ends of upper branches and have a backwards pointing hood (up to 37 mm long). Hairless, ribbed seed capsules (2-3 cm long) are usually purplish on exposed side and open when disturbed, explosively releasing shiny black seeds (3.5-5 mm long).
Are there any similar species?
Shrub balsam (I. sodenii) is a much-branched, shrub-like perennial herb with simple, flat, pale pink-mauve flowers (5-6.5 cm diameter). Garden balsam (I. balsamina) has flowers on short stalks off the main stem and densely hairy seed capsules. Alternatives: Try a native hebe, or a non-native winter rose (Helleborus species). Your local garden centre will be able to recommend other non-weedy alternatives that will grow well in your area.
Why is it weedy?
Tall and fast growing plant capable of producing up to 2500 seeds that are spread quickly by water and can be viable for 18 months or more. It competes with native plants for light, space and pollinators (bee) and spreads into river edges, gullies, wetlands, forest margins and other similar areas.
How does it spread?
Reproduction is by seed only. Seeds float and are spread by water movement.
What damage does it do?
Competes with native plants for light, space and pollinators (bees). It can dominate the vegetation on stream banks, leaving them bare over winter and prone to erosion.
Which habitats is it likely to invade?
River edges, riparian areas, gullies, wetlands, forest margins, roadsides and ditches. It prefers moist soil and full sun to light shade.
What can I do to get rid of it?
1. Hand pull seedlings and small patches before seeding (spring to summer). Dispose of at refuse transfer station.
2. Cut stems (spring to summer): cut close to the soil below the first node (leaf joint) before seeding. Dispose of at refuse transfer station. Repeat treatment in summer if any regrowth from stumps.
3. Overall spray (full leaf): glyphosate (10 ml/L + penetrant) or metsulfuron-methyl 600g/kg (4 g/15L).
What can I do to stop it coming back?
Monitor the site for two years, treating any regrowth from stumps or seedlings.