Ludwigia (Ludwigia peruviana)

Also known as: Peruvian primrose, water primrose, primrose willow

Ludwigia is a fast-growing wetland shrub with bright yellow flowers. It outcompetes native plants and reduces the amount of food and habitat for fish and native animals.

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How does this weed affect you?

Ludwigia is a fast-growing invasive aquatic weed. It forms dense colonies in slow-moving and static waterways. It:

• changes the water flows in waterways and can increase the risk of flooding
• outcompetes native plants
• reduces food and shelter for fish and other native aquatic animals
• decreases light and water temperature
• limits recreation activities including boating
• can limit livestock access to the water

What does it look like?

Ludwigia is an upright perennial shrub up to 3 m tall. It is deciduous in cooler climates and evergreen in warmer tropical climates. It can form floating islands on the water surface.

Leaves are:

• usually 5–10 cm long and 1–3 cm wide
• oval to lance-shaped with a pointed tip and narrow base
• hairy
• prominently veined
• usually alternate along the stem.

Flowers are:

• bright yellow
• single, growing in the fork of upper leaves
• usually with 4 petals (sometimes 5 or 6), each up to 3 cm wide and long
• surrounded by 4 pale green leaf-like structures below the petals (sepals)
• each flower lasts for only one day
• present during late summer-autumn.

Seedpods:

• are reddish-brown with reddish sepals that stay attached to the pod
• are 1–2 cm long and 6–10 mm wide
• are erect and squarish in cross-section
• contain 1000–4000 seeds.

Stems are:

• dark green to brownish green
• round in cross-section
• branched
• hairy when young.

Roots:

• a large taproot is produced when the plants are still seedlings
• older plants have a woody tap root 
• lateral roots grow close to the surface. 

Similar looking plants

Ludwigia looks like:

• Long-leaf willow primrose (Ludwigia longifolia), an introduced species, which has red, hairless stems that are squarish in cross-section. the leaves are also hairless.
• Willow primrose (Ludwigia octovalvis), a native species, which has longer fruit (up to 4.5 cm) that are rounded in cross-section. The leaves may be longer (up to 15 cm) and are often narrow.
• Water primrose (Ludwigia peploides subsp. montevidensis), a native species, which has a creeping or floating  habit. The leaves are mostly hairless and the flowers usually have 5 petals and sepals.

Where is it found?

In NSW, Ludwigia has mostly been found in creeks and wetland areas of the Greater Sydney region. A few plants have also been found in the Hunter and South Eastern regions.

It is native to South America and was introduced as an ornamental plant.

What type of environment does it grow in?

Ludwigia grows in humid, warm temperate, subtropical and tropical climates. It establishes in moist or wet areas along creek banks, in swampy marshes and wetlands. It can grow in still or slow-moving water.

Maps and records

• Recorded presence of Ludwigia during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

By seed

Plants produce seeds after 18 months of age. The seeds have high viability of about 80% and most germinate in spring. Seeds are mostly spread by flowing water and birds. The sticky seeds are also spread by attaching to clothing, feathers, hair and machinery. Ducks eat and spread the seeds. Seeds can germinate in as little as 4 days in shallow clear water, while floating or in mud.

By plant parts

Ludwigia reproduces vegetatively from roots and stems. Root and stem fragments can break off and spread downstream. Entire stands of mature plants can be dislodged in floodwaters and can take root in a new area downstream. 

References

Department of the Environment (2011) Weeds in Australia: Ludwigia peruviana, Australian Government. Available at www.environment.gov.au

Identic and Lucid. (2016). Weeds of Australia Factsheet: Ludwigia peruviana (L.) Hara. Retreived April 2023 from https://keyserver.lucidcentral.org/weeds/data/media/Html/ludwigia_peruviana.htm

Parsons, W.T. and Cuthbertson, E.G. (2001). Noxious weeds of Australia, CSIRO Publishing, Collingwood.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved April 2023 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Ludwigia~peruviana

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

More information

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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.

Control ludwigia seedlings in the first 18 months of growth, before flowering to manage the soil seed bank.  

Prevention

Plant riparian vegetation that can outcompete Ludwigia. Reducing nutrient runoff into the waterway can limit growth. To stop the spread of seeds prevent public and machinery access to sites with Ludwigia. 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. Follow up with herbicide may be required.

Disposal

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

Slashing/Fire

Larger infestations may be slashed and burnt.

Chemical control

Spraying

When using glyphosate, spray when the plant is actively growing at or beyond the early bloom stage of growth but before autumn change of colour. Apply to all foliage to the point of visible wetness.

The permit has restrictions on who can use it. Check the permit before use.

Cut stump method

Cut the main stems, and apply herbicide gel to the stump within 15 seconds of cutting.

Herbicide options

See Using herbicides for more information.

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PERMIT 87496 Expires 31/05/2024
2,4-D amine 500 g/L (Various products)
Rate: 125 mL in 100 L of water
Comments: This permit is only for State and local government employees, licensed contractors and employers working for state and local government organisations. See permit for further conditions and critical comments. Apply as direct application to foliage, minimising runoff from leaf surface. Do not apply as a broadcast spray over water.
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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PERMIT 87496 Expires 31/05/2024
2,4-D amine 625 g/L (Various products)
Rate: 100 ml in 100 L of water
Comments: This permit is only for State and local government employees, licensed contractors and employers working for state and local government organisations. See permit for further conditions and critical comments. For best results apply in the vegetative/ stem elongation stage
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: 1 L in 100 L of water
Comments: Actively growing at or beyond the early bloom stage of growth but before autumn change of colour. Thorough coverage is necessary for best results.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Picloram 44.7 g/L + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump application. Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm .
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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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 pest 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 West	Regional Recommended Measure* (for Regional Priority - Prevention) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Greater Sydney	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Notify local control authority if found.
Hunter	Regional Recommended Measure* (for Regional Priority - Eradication) Notify local control authority if found. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant.
North Coast	Regional Recommended Measure* (for Regional Priority - Prevention) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
North West	Regional Recommended Measure* (for Regional Priority - Prevention) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
South East	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. 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

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Reviewed 2023