Erect, perennial herb < 3 m tall. Roots are fibrous and form dense surface mats. Stems are usually many-branched and square. Leaves are < 12 cm long, lanceolate-ovate, narrow, opposite or in whorls and clasped around the stem. Flowers are purple and borne in dense, < 25 cm long flower spikes in December-February. Seeds are minute, numerous and borne in blackish capsules.
To help protect our environment:
Still or slow-moving water bodies, wetlands, riparian margins, lakes, ditches, reservoirs.
Seeds dispersed by wind, water, waterfowl and soil movement. Vegetative spread from root fragments. Human-mediated dispersal through dumping of garden waste, deliberate plantings and movement of contaminated machinery, vehicles and clothing.
Forms dense stands, outcompeting and displacing native vegetation. Impedes waterfowl and access to waterways.
Follow up treated areas 3 times per year. Encourage natural regeneration of native plants or replant treated areas where possible after 2-3 treatments to establish dense ground cover and minimise reinvasion.
CAUTION: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.