Alisma lanceolatum, commonly known as lanceleaf water plantain or narrow-leaved water plantain, is a perennial herb native to shallow freshwater habitats such as marshes, ponds, and the margins of slow-moving streams across Europe, North Africa, and temperate Asia. It has also become naturalized in parts of Australia, New Zealand, and North America, including Oregon, California, and British Columbia. The plant typically reaches about 2.3 feet in height with a spread of 0.8 feet. It features lance-shaped leaves on long petioles and erect inflorescences up to 20 inches tall, bearing small, showy pinkish-purple three-petalled flowers during the summer months.

Lanceleaf water plantain is valued for its ornamental flowers and its ability to thrive in aquatic environments, making it a popular choice for water gardens and naturalized pond edges. It is also used in constructed wetlands for water purification. In cultivation, it requires full sun to part shade and prefers to be planted in shallow water or consistently wet mud. It is hardy in USDA zones 5-8 and can spread by seed or by rhizomes, which can sometimes lead to aggressive growth in ideal conditions. While generally low-maintenance, it can be susceptible to rust and other fungal diseases.CC BY-SA 4.0