Long-leaf willow primrose (Ludwigia longifolia)

Long-leaf willow primrose is an aquatic shrub with yellow flowers. It forms dense stands in slow-moving or still water.

Profile

How does this weed affect you?

Long-leaf willow primrose is an aquatic weed that could invade large areas of NSW waterways and wetlands. It forms dense colonies in slow moving and static waterways. It:

  • outcompetes native plants
  • reduces food and habitat for fish and other aquatic animals
  • changes water flow and increases flood risks
  • limits access to waterways.

What does it look like?

Long-leaf willow primrose is an upright annual shrub up to 3 m tall that grows in wet areas and in water.

Leaves are:

  • long and thin with a pointed tip
  • 10–20 cm long and 0.5–2.5 cm wide
  • larger lower down and smaller higher up the stem
  • stalkless
  • alternate on the stems.

Flowers are:

  • yellow with 4 (or rarely 5) petals each 2.0–2.5 cm long and 4 red or green sepals
  • single in the junctions of upper leaves
  • present from summer–winter.

Seedpods are:

  • 10–42 mm long and 4–8 mm wide
  • oblong to narrow-oblong
  • 4-angled with lots of seeds in separate chambers.

Seeds are:

  • brown to yellow
  • less than 1 mm long
  • abundant and dust-like.

Stems are:

  • red or greenish
  • narrow and square shaped often with winged edges
  • usually branching towards the top.

Roots are:

  • shallow
  • fibrous.

Similar looking plants

Long-leaf willow primrose looks like other Ludwigia species:

  • Mexican primrose-willow (Ludwigia octovalvis), a native species, which has hairy stems, leaves and fruit and almost round stems.
  • Water primrose (Ludwigia peploides subsp. montevidensis), a native species, which has a creeping habit and small leaves up to 6 cm long.
  • Peruvian water primrose (Ludwigia peruviana), an introduced weedy species, which has hairy stems, leaves and fruit with shorter, broader leaves.

Where is it found?

Long-leaf willow primrose grows on the NSW coast and in some inland areas. Most infestations in NSW are in the Greater Sydney and Hunter regions. It has also been found on the North Coast from Ballina to Port Macquarie and near Brisbane in Queensland.

It is native to South America. It was introduced to Australia as an aquatic ornamental plant and was first recorded as naturalised near Sydney in 1991.

What type of environment does it grow in?

Long-leaf willow primrose grows in sandy, silty soil in water bodies, including wetlands and riparian areas, swamps, marshes, drains and channels.

Maps and records

How does it spread?

By seed

Most spread is by seeds. Mature plants can produce up to 2.45 million seeds per plant. Seeds are spread in moving water, wind and by birds. They can also spread by contaminated soil or mud stuck to machinery, vehicles, footwear or clothing.

By plant parts

Long-leaf willow primrose is occasionally spread by broken stem fragments that are moved in flood waters.

References

Chandrasena, N. (2005). Ludwigia peruviana (L.) Hara and Ludwigia longifolia (DC.) Hara in Sydney: from immigrants to invaders. In Proceedings of the 20th Asia-Pacific Weed Science Society Conference.(Eds M. Mortimer, K. Itoh, T. Phuc Tuong, L. Cam Loan & N. Hong Son). Ho-Chi-Minh City, Vietnam (pp. 121-130).

Identic Pty Ltd. and Lucid central (2016). Environmental Weeds of Australia Fact sheet: Ludwigia longifolia (DC.) H. Hara. Retreived August 2021 from https://keyserver.lucidcentral.org/weeds/data/media/Html/ludwigia_longifolia.htm

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 24 August 2021 from https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Ludwigia~longifolia

Sainty, G. R., & Jacobs, S. W. (2003). Waterplants in Australia (No. Ed. 4). Sainty and Associates Pty Ltd.

More information

back to top

Control

Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

To manage long-leaf willow primrose:

  • contact your local council weeds officer to seek advice on identification and control methods
  • use physical removal for small, isolated infestations before they set seeds[CM1] 
  • if plants are seeding collect and bag seed heads and dispose of appropriately
  • plant native riparian species to compete with and reduce regrowth
  • limit access to the site from the public, animals and machinery.[CM2] 

Prevention

Plant riparian vegetation that can outcompete long-leaf willow primrose. Reducing nutrient runoff into the waterway can limit growth. To stop the spread of seeds prevent public and machinery access to sites with long-leaf water primrose. If possible limit animal access to the sites as well.

Physical removal

Seedlings can be pulled or dug 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.

Disposal

Plants can be destroyed by burning or deep burial. Contact your local council for further advice on how to dispose of this weed.

Chemical control

Spot spraying

When: Apply herbicides from 1 September till 30 June or before flowering.

Apply to all foliage to the point of visible wetness.

Once plants have been killed by herbicides, follow up burning can be useful.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


PERMIT 14731 Expires 30/06/2024
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: 1.0 L per 100 L of water
Comments: Spot spray application. Apply from 1st September to 30th June, or before flowering occurs. See permit for more critical use comments.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


back to top

Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Central Tablelands Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Central West Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Hunter
Core infestation area:Newcastle, Lake Macquarie, Port Stephens and Mid Coast. Exclusion zone: Rest of region
Regional Recommended Measure* (for Regional Priority - Containment)
Whole of region: The plant should not be bought, sold, grown, carried or released into the environment. Within Exclusion zone: Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. Within Core Infestation: Land managers to reduce impacts from the plant on priority assets.
North Coast
Exclusion zone: All lands in the region except the core infestation area of Nambucca Shire Council, Bellingen Shire Council, Coffs Harbour City Council, Clarence Valley Council, Richmond Valley Council, Ballina Shire Council, Lismore Council, Kyogle Council, Byron Shire Council and Tweed Shire Council.
Regional Recommended Measure* (for Regional Priority - Containment)
Whole region: The plant or parts of the plant should not be traded, carried, grown or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should reduce impacts from the plant on priority assets.
North West Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
South East Regional Recommended Measure* (for Regional Priority - Eradication)
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

back to top


For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW DPI Biosecurity Helpline on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2021