Najas guadalupensis, commonly known as Southern Naiad or Southern Waternymph, is an annual aquatic herb native to a wide range of freshwater habitats including ponds, lakes, slow-moving streams, and canals throughout the Americas, from Canada to South America. It has also been introduced to parts of Asia and the Middle East. This submerged plant features slender, branching stems that can grow up to 35 inches long, with leaves arranged in opposite pairs along the stem. The leaves are typically 1 inch long and have finely serrated margins, which can give them a comb-like appearance.

Southern Naiad is valued for its use in aquariums and ponds due to its ability to oxygenate water and provide habitat for aquatic wildlife. It is also used in water gardens and can help control algae by competing for nutrients. In cultivation, it requires full sun to part shade, and it can grow in a variety of water conditions, from stagnant to slow-flowing, with a preference for soft, slightly acidic to neutral pH levels. However, it is potentially invasive outside its native range and can form dense mats that disrupt water flow and outcompete native species. Gardeners should check local regulations before cultivating Najas guadalupensis to ensure it is not considered invasive in their area.CC BY-SA 4.0