Ludwigia (Ludwigia peruviana)

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

Ludwigia is an invasive shrub. It thrives in moist, wetland environments and has a dramatic impact on the aquatic environment.

Profile

How does this weed affect you?

Ludwigia is fast growing and produces thousands of sticky seeds. Ludwigia can choke waterways and dominate all aquatic vegetation within a short timeframe. Dense stands can interfere with the natural flow of the waterway. The thick canopy reduces the amount of light entering the water and decreases water temperature. This ultimately affects the native aquatic flora and fauna communities.  

Ludwigia has the potential to become a serious weed of wetlands and other riverine habitat throughout tropical and sub-tropical Australia.

Where is it found?

Native to South America, from Mexico through to Chile. Ludwigia has been used as a wetland and garden ornamental in many countries. It is a weed in India, Indonesia, Malaysia and the USA. 

In Australia, ludwigia is only known to exist in creek and wetland areas of the Sydney region.  Thick infestations exist in the Botany wetlands where is has invaded about 30 ha of land and taken over most of the original habitat. Smaller and localised outbreaks have occurred in Hornsby, Gosford and Port Stephens along drainage channels, creeks and lagoons. Ludwigia is a threat to many endangered freshwater wetlands areas in the Sydney bioregion.

Distribution map

• NSW (image)

How does it spread?

Ludwigia reproduces by seed and vegetatively from root suckers. Seed is mostly spread by flowing water and birds. The sticky seeds are also spread by attaching to clothing, feathers, hair and machinery.

Root and stem fragments can break off and spread downstream. Entire ‘islands’ of mature plants can become dislodged in flood waters, which can take root again in a new location downstream.  

Lifecycle

Seeds germinate in spring in the mud along the waters edge, on the mats of floating vegetation ‘islands’ and in shallow water. Rapid growth is experienced throughout summer. Seedlings produce a large taproot, anchoring it to the soil. Plants do not flower for two years following germination. They then flower annually, late summer and autumn.

Each fruit capsule contains 1000–4000 seeds with about 80% viability. Seeds are able to germinate in as little as 4 days in shallow clear water, while floating or in mud. 

What does it look like?

Ludwigia is a perennial shrub growing up to 3 m high. It behaves as a deciduous plant in cooler climates and an evergreen in warmer tropical climates.

Stem

• hairy when young
• dark green to brownish green in colour
• branched

Leaves

• arranged alternately along the stem
• egg to oval-shaped with pointed tip
• 5–10 cm long and 1–3 cm wide
• hairy
• prominent veins

Flower

• bright yellow, 2-4 cm across
• a single flower grows in the fork of upper leaves
• 4 petals (sometimes 5 or 6), each 1-3 cm long and 1-3 cm wide
• 4 pale green sepals—leaf-like structures below petals
• last only one day

Fruit

• reddish-brown in colour
• a capsule
• 10–25 mm long and 6–10 mm wide
• reddish coloured sepals remain attached
• contains thousands of seeds

Seed

• light brown
• 0.6–0.8 mm long

What type of environment does it grow in?

Ludwigia is capable of growing in humid, warm temperate, sub-tropical and tropical climates. Grows in moist or wet areas along creek banks, in swampy marshes and wetlands. Capable of growing in stationary or slow-moving water. Able to float on the water surface and form floating ‘islands’.

References

Department of Employment, Economic Development and Innovation (2011) Peruvian water primrose: Lugwigia peruviana, Queensland Government. Available at http://keyserver.lucidcentral.org/weeds/data/ 03030800-0b07-490a-8d04-0605030c0f01/media/Html/Ludwigia_peruviana.htm. Accessed August 2014.

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

Ensbey, R (2011) Noxious and environmental weed control handbook. NSW Department of Primary Industries, Orange. Available at http://www.dpi.nsw.gov.au/agriculture/pests-weeds/weeds/publications/ noxious-enviro-weed-control. Accessed August 2014.

Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK.

Parsons, WT and Cuthbertson, EG (2001) Noxious weeds of Australia, CSIRO Publishing, Collingwood.

back to top

Control

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

Physical control

Small ludwigia plants can be manually pulled or hoed from the ground. Remove as much of the root as possible. Larger infestations may be slashed and burnt. Follow up with herbicide may be required. Always take care not to spread seed.

Herbicide control

Treat plants with a registered herbicide when actively growing and before flowering. Apply using foliar spray, cut stump or stem injection, depending upon the chosen herbicide. Follow up control will be necessary.

Herbicide options

See Using herbicides for more information.

---

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: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

---

Picloram 44.7 g/kg + 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: I, Disruptors of plant cell growth (synthetic auxins)
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* 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* 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.
Greater Sydney	Regional Recommended Measure* Land managers mitigate the risk of the plant being introduced to their land. Land managers prevent spread from their land where feasible. Land managers reduce the impact on priority assets. The plant should not be bought, sold, grown, carried or released into the environment. Local Control Authority is notified if the plant is found on the land.
Hunter Land Area 1: Core infestation area of Port Stephens and Lake Macquarie. Land Area 2: rest of region	Regional Recommended Measure* Land Area 1: Land managers should mitigate the risk of new weeds being introduced to their land. Land Area 2: The plant should be eradicated from the land and the land kept free of the plant. Notify the Local Control Authority if found. The plant should not be bought, sold, grown, carried or released into the environment.
North Coast	Regional Recommended Measure* 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.
North West	Regional Recommended Measure* 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* 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 fulfill the general biosecurity duty for this weed click here

back to top

Reviewed 2018