Water primrose is known to form dense plant mats which fill in wetlands and slow-moving water bodies, slowing them down further or stopping the flow completely. Shoreline root mats can be 1-2 feet deep, preventing all other plants from rooting. This view of water primrose infestations is pretty typical:

Do you see any open water? Right. Clogged waterways are associated with several problems:

• Reduced plant and animal diversity as other species are displaced
• Poorer drainage flows as mats slow water and accumulate sediment
• Lower water quality as dissolved oxygen is used up
• Fewer recreation opportunities, like fishing or swimming

Managing water primrose is also difficult. The plants are often too deeply rooted (and heavy!) to easily, or effectively, hand-pull. Ludwigia species spread primarily by fragments, and, to a lesser degree, by seed. Both seeds and fragments are moved around by running water and waterfowl.