Quick Facts

Quick facts

  • Ludwigia (Ludwigia peruviana) is a shrub that spreads by seed and stem segments.
  • Once established, seedlings grow vigorously, forming tall, dense bushes that out compete other species.
  • Ludwigia reduces the rate of flow in streams and causes wide ecological damage by increasing sedimentation and decreasing oxygen levels.
  • Management should be focused on seedlings and the soil seed bank to control the source of dispersal before the rate of spread becomes too great.

What Does It Look Like?

What is it?

Ludwigia (Ludwigia peruviana) is a shrub which grows to 3 m high. The stems are hairy especially when young. The leaves are alternately arranged, egg-shaped to lanceolate, 4–12 cm long and 3–15 mm wide and sessile (without a stalk). The flowers are yellow, solitary in the leaf axils (where the leaf meets the stem), with 4 or occasionally 5 petals that are 1–3 cm long. The fruit is an erect hairy capsule, 1–2 cm long with the rusty red sepals remaining attached to the upper rim. Seeds are light brown and numerous (Sainty & Jacobs 1981; Parsons & Cuthbertson 2001; Harden 2007)

For further information and assistance with identification of Ludwigia contact the herbarium in your state or territory.

Flower colour


Growth form (weed type/habit)

Shrub, Aquatic

Where it currently grows? Preferred habitat

Ludwigia grows in humid warm-temperate to tropical regions. It occurs in stationary or moving fresh water to 1 m deep in lagoons, swamps, or on the margins of creeks and rivers (Sainty & Jacobs 1981; Parsons & Cuthbertson 2001). In deeper waters, the plant survives by producing pneumatophores (erect roots that protrude above the surface) that enable air to be carried to the submerged tissues (Jacobs et. al. 1994). In shallow permanent water, the plant encroaches on open water by gradually forming a mat of fallen stems and trapped debris. From the fallen stems, new stems grow upright to form dense shrubs (Jacobs et. al. 1994).

Are there similar species?

Ludwigia can be confused with the native species Ludwigia peploides ssp. montividensis which has a long narrow fruit, floating stems which root at the nodes and a longer leaf petiole than Ludwigia. The introduced species Long-leaved Water Primrose (Ludwigia longifolia) is similar to Ludwigia but does not have hairs on its stems, leaves or fruit (Harden 2007).

Why Is It A Weed?

What are its impacts?

Ludwigia reduces the rate of flow in streams and causes wide ecological damage by increasing sedimentation. The accumulation of additional organic material results in the deoxygenation of the water column which leads to the death of aquatic fauna and a change in flora species composition. Dense stands of Ludwigia can intercept almost all light, dominate all other water plants and in some cases lead to the loss of native plants and animals. In areas where it has been established longest, such as the Botany Wetlands, monospecific stands have formed, native water plants have been crowded out, and bird populations have diminished (Jacobs et al. 1994).

Ludwigia has the potential to interfere with animal access for drinking water, human access for swimming and boating, reduce water quality and block pumps (Campbelltown City Council undated).

How does it spread?

Ludwigia disperses by seed and vegetatively from stem pieces. New plants from seed, seedlings or stem fragments may become established on strand lines or form floating islands that eventually become stranded. These islands continue to grow (to 15 m in diameter in the Botany Wetlands) and eventually take root on the bottom in shallow water. A flood may detach an island which can float off to become established elsewhere. Ludwigia is one of the few shrubby species in which mature plants may be dispersed. Seeds can be readily dispersed by adhesion to clothes, hair, feathers and machinery. Wet seeds may be picked up by birds and transported to other wetland areas (Jacobs et. al. 1994).

What is its history in Australia?

Ludwigia was cultivated at the Royal Botanic Gardens, Sydney, in 1907. It was first recorded as naturalized in Australia in the Botany Wetlands in 1970 and was recognized in 1971 as a potential weed (Jacobs et. al. 1994).

How To Manage It?

Best practice management

Management of Ludwigia needs to focus on the control of the seedlings and the soil seed bank as it is important to control the major source of dispersal before the rate of spread becomes too great. Flowering and fruiting do not usually occur in the first year, so the plants can be controlled at any time in the first 18 months without the risk of seed set. Germination can be suppressed by high degrees of shading. The soil seed bank may be greatly reduced after two or three years without input. The plant appears to be susceptible to drying out and new shoots appear to be susceptible to flooding (Jacobs et. al. 1994).

Apply herbicides when the plant is actively growing at or beyond the early bloom stage of growth but before theautumn change of colour. Thorough coverage is necessary for best results. Spraying results can be improved by slashing stands prior to flowering, then spraying the regrowth 2–4 weeks later. Repeat applications may be required for larger plants, and a follow up program will be required to deal with seedlings. Care should be taken not to inadvertently spread seed attached to clothing (NSW Agriculture undated).

No known research has been conducted on introduced biological control agents and the species is not currently a Target for Biological Control. There is some evidence of ecological control by shading under dense planting. Because Ludwigia seedlings require high light levels for germination, it can be appropriate in some locations to establish dense, shady cover following clearing. In the long term, reducing nutrient levels entering water bodies can also lower the risk of invasion or spread (NSW Agriculture Undated).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

The seeds of Ludwigia germinate in spring and summer growth is rapid, with the seedlings producing a strong secure tap root anchoring them to the soil. The period between germination and flowering is about 2 years. Established plants flower annually from summer to autumn (Parsons & Cuthbertson 2001). The plant is evergreen in its native habitat, but is reported to lose its leaves during winter in the Sydney area. (Sainty & Jacobs 1981).

Seed production is large and seeds germinate in 4 days in shallow clear water or mud; at least 80% of the seed produced is capable of germinating. Seeds will germinate while floating. Germination appears limited by depth of soil, with few growing to the surface through sand 1 cm deep (Thorp & Wilson 1998 – ). The fruit remains on the plant over winter and seed dormancy appears to breaks down within 2 years (Sainty & Jacobs 1981).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Ludwigia occurs in New South Wales in the greater Sydney region. It is confined mostly to the coast, but it is also recorded from the Wollondilly area (Harden 2007).

Where does it originate?

Ludwigia is native to central and South America (Jacobs et. al. 1994).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Ludwigia peruviana

Other scientific names (synonyms)?

Jussiaea peruviana L.

Does it have other known common name(s)?

Water Primrose, Primrose Willow, Peruvian Primrose, Willow Primrose

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