Ecological Risk Screening Summary - Large-flower Primrose-willow (Ludwigia grandiflora) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.

Ludwigia grandiflora, large-flower primrose-willow, is a flowering plant that is native to South and Central America and possibly parts of the United States. Ludwigia grandiflora grows quickly, covers large areas and forms dense mats, leading to negative impacts on water quality, native biodiversity, human and fish navigation, and recreational activities. Within the United States, L. grandiflora is regulated in seven states. The History of Invasiveness for Ludwigia grandiflora is classified as High due to L. grandiflora being established outside its native range and a plethora of clear, convincing, and reliable documentation of negative impacts of introduction. The climate matching analysis for the contiguous United States indicates establishment concern for this species. Areas with the highest climate match were located in the Southeast, Northeast, southern Midwest, and along the Pacific coast. The Certainty of Assessment is classified as High due to the abundant, clear, and convincing information available about Ludwigia grandiflora’s distribution and negative impacts of introduction from peer-reviewed scientific literature. The Overall Risk Assessment Category for Ludwigia grandiflora in the contiguous United States is High.