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Water chestnut (Trapa natans)
Photo credit: Jardin des Plantes, Paris; CC-BY-SA 3.0

Water Primrose

(Ludwigia grandiflora ssp. hexapetala)

Report this Species!

If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

L. grandiflora is a productive emergent perennial native to South and Central America and parts of the USA. In the USA, it has caused severe problems (IPAMS, 2009). In its adventive range, L. grandiflora can transform ecosystems both physically and chemically. It can sometimes be found growing in impenetrable mats; under these conditions, L. grandiflora can displace native flora and interfere with flood control and drainage systems, clog waterways and impact navigation and recreation (IPAMS, 2009). The plant also has allelopathic activity that can lead to dissolved oxygen crashes and the accumulation of sulphide and phosphate in the water. These not insubstantial and year-round effects on water quality can cause ‘dystrophic crises’ and intoxicated ecosystems (Dandelot et al., 2005).

Similar Species

Depending on its life stage, water primrose may be confused with many native floating and emergent Ludwigia species.


As an aquatic species, water primrose prefers to grow in riparian and lacustrine habitats.


In North America, water primrose was first introduced outside its native range into Tennessee and Kentucky with the collection of specimens occurring in 1968 and 1988 respectively. Currently, water primrose is found mostly in the southern United States, but also in Pennsylvania where it's been reported in Berks County.

Environmental Impacts

Water primrose is a rooted aquatic species that invades natural areas via stolons (i.e., "runners") that spread on land and water surfaces. It rapidly forms a floating mass that chokes out native flora and clogs waterways. Recreational activities are impaired and biodiversity is severely threatened due to this plant.

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