Long leaf Willow Primrose is an annual plant native to Argentina and Brazil but now naturalized many countries in the world including India and Australia. It also commonly found in Sri Lanka, widely naturalized in wet zone and dry zone. The plant is a one of exotic species of Ludwigia genus which is called several Sinhala names including Beru Diyanilla, Diya Milla, and Boru Diya Milla. It is one of the most common weeds on adjacent to water bodies that extremely invasive plant considered one of most troublesome weed in irrigated paddy fields and also threatens the native plants and the natural ecosystem.
Other exotic species of the genus Luwigia : Ludwigia peruviana
Native species of Ludwigia genus : Ludwigia adscendens, Ludwigia perennis, Ludwigia hyssopifolia, Ludwigia prostrata and Ludwigia octovalvis.