Longroot Smartweed (Water Smartweed)

Other Common Names: water smartweed

(Polygonum amphibium, Pesicaria amphibia)


Longroot smartweed, or water smartweed, has sword shaped leaves up to five inches long and tiny rose pink flowers atop a spike. It grows on land or in water.


There are two forms of longroot smartweed: terrestrial, in which the stems only grow to three feet tall, and aquatic, in which the stems can be as tall as six feet. Stems are slightly swollen above the nodes, which is also where this plant roots. Stems may branch sparingly. Leaves are sword shaped, two to five inches long and can be four-tenths of an inch to more than two inches wide. Each plant bears one to two flower spikes that contains many flowers packed together. Flower spikes grow four-tenths of an inch to more than three inches tall. The flower stalk can be four-tenths of an inch to an inch tall and is red and fleshy. Only one flower blooms at a time and is rose pink. Flowers have five lobes and grow less than two-tenths of an inch long.


Longroot smartweed grows in still or slow moving water and mud in wet meadows. Ducks, small birds, and small mammals feast on smartweed seeds.


Longroot smartweed can be found in nearly all 50 states of the United States.


seeds, roots