Also known as
Yellow bladderwort, dwarf bladderwort, Utricularia biflora, U. exoleta
Where is it originally from?
What does it look like?
Mat-forming, algae-like perennial that is submerged just below the surface of the water or entangled with other plants. It doesn't have roots, and stems are very thin with filament-like leaves that are single or paired with bladders (1-2mm long) along their full length that trap insects. From December to January yellow flowers (6 mm diameter) are produced that protrude up to 20 cm above the water surface.
Are there any similar species?
Four native Utricularia species, three of which are terrestrial. Rare U. protrusa has many-branched, filamentous leaves, 2-3 mm long bladders, 9 mm diameter flowers (rarely seen) and is found only in still, nutrient-poor water.
Why is it weedy?
Reproduces freely, disperses widely and forms dense mats. Tolerant of clean or nutrient-rich, warm or cold, still or slow-moving water.
How does it spread?
Seeds, turions (hibernating buds) and stem fragments are spread by water movement, dumped aquaria contents, contaminated machinery, eel nets, boats and trailers, intentional planting, and possibly birds.
What damage does it do?
Spreads rapidly, forms mats from the surface of the water to 6+ metres down, and displaces native species that are not as wide-ranging. Rotting vegetation ruins water quality.
Which habitats is it likely to invade?
Most freshwater habitats, especially acidic and nutrient rich water, and could potentially establish throughout New Zealand.
What can I do to get rid of it?
Firstly establish that the plant is not a native species.
1. Rake up: Leave on site to rot down. away from damp areas and water.
2. Lower water level, mechanically remove or use weedmat.
What can I do to stop it coming back?
Plant trees along narrow waterbodies to create shade. Prevent nutrient runoff by planting riparian strips and removing source of pollution.