Native to South America Long Leaf Willow Primrose was introduced to Australia as an aquatic ornamental plant and was first recorded as naturalised near Sydney in 1991.
Long-leaf willow primrose is an upright annual shrub with long, thin pointed leaves and a 4 petal buttercup flower, able to grow to 3 m tall in sandy, silty soil in water bodies, including wetlands and riparian areas, swamps, marshes, drains and channels.
An aquatic weed Long-leaf willow primrose can invade large areas of NSW waterways and wetlands, forming dense colonies, outcompeting native plants, reducing food and habitat for fish and other aquatic animals, it can change water flow and increase flood risks.
It spreads by seed with mature plants producing up to 2.45 million seeds per plant. Seeds spread in moving water, wind and by birds. They can also spread by contaminated soil or mud stuck to machinery, vehicles, footwear or clothing.
Best Control methods
It can be controlled by physical removal by pulling or digging it out. Avoid breaking the plant and leaving behind pieces that could start new infestations. It is best to remove plants before they set seed to avoid spreading the seeds. Applying herbicides can be done from 1st September till 30th of June or before flowering. Refer to local council before using chemicals.
Further information and control options are detailed in the NSW WeedWise app, which is free to download, or on the website here: NSW WeedWise.
If you find this weed on your property, Council’s Biosecurity Officer is happy to provide advice to help you bring this nasty weed under control.
Similar but native
Long-leaf willow primrose looks like other Ludwigia species.
The Mexican primrose-willow (Ludwigia octovalvis), pictured left, is a native species, which has hairy stems, leaves and fruit and almost round stems