Persicaria amphibia (L.) Delarbre  

Family: Polygonaceae

water knotweed

[Persicaria amphibia var. emersum,  more, Persicaria amphibia var. stipulacea (N. Coleman) H. Hara, Persicaria pratincola Greene, Polygonum amphibium L., Polygonum amphibium f. fluitans (Eaton) Fernald, Polygonum amphibium f. simile Fernald, Polygonum amphibium var. emersum Michx., Polygonum amphibium var. hartwrightii (A. Gray) Bissell, Polygonum amphibium var. stipulaceum , Polygonum coccineum Muhl. ex Willd., Polygonum coccineum f. natans (Wiegand) Stanford, Polygonum coccineum f. terrestre (Willd.) Stanford, Polygonum coccineum var. coccineum , Polygonum coccineum var. pratincola (Greene) Stanford, Polygonum coccineum var. rigidulum (Sheldon) Stanford, Polygonum natans Eaton, Polygonum natans f. genuinum Stanford, Polygonum rigidulum Sheldon]