Emergent Water Plantain, Grass-leaved Water-plantain, Narrowleaf Waterplantain, Narrowleaf Water-plantain: Alisma gramineum var. angustissimum (Synonyms: Alisma geyeri, Alisma gramineum, Alisma gramineum var. angustissimum, Alisma gramineum var. geyeri, Alisma gramineum var. gramineum, Alisma validum) - Flowers small with white to rose petals. Petals less than 4 mm long. Inflorescence a panicle not rising above the leaves. Lower panicle branches usually with only one whorl of branchlets. Leaves less than 2 cm wide, linear to narrowly elliptic.
American Waterplantain, American Water-plantain, European Water-plantain, Northern Water-plantain: Alisma triviale (Synonyms: Alisma plantago-aquatica, Alisma plantago-aquatica var. americanum, Alisma plantago-aquatica var. plantago-aquatica) - Flowers small with white to rose petals, each 4-6 mm long. Inflorescence a panicle of 3-6 (or more) whorls which rises above the basal leaves. Lower panicle branches with 2 to many whorls of branchlets. Tips of petals entire to slightly toothed. Leaves more than 2 cm wide, more or less elliptic in shape or lanceolate to ovate.
California Damasonium, Fringed Waterplantain, Fringed Water-plantain, Star Water-plantain: Damasonium californicum (Synonym: Machaerocarpus californicus) - Flowers large (petals 7-10 mm long). Inflorescence a simple umbel or a 2-4 whorled panicle. Leaf blades linear to oblong-lanceolate with rounded bases, 3-8 cm long. Tips of petals deeply cut to fringed.
Arumleaf Arrowhead, Arum-leaf Arrowhead, Wapato: Sagittaria cuneata (Synonym: Sagittaria arifolia) - Mostly east of the Cascade Mts. Arrowhead-shaped leaf blades mostly 6-15 long and 2-10 cm wide. Inflorescence often branched, the flowers in 3-7 whorls.
Broadleaf Arrowhead, Broad-leaf Arrowhead, Common Arrowhead, Duck Potato, Wapato: Sagittaria latifolia (Synonym: Sagittaria latifolia var. latifolia) - Mostly west of the Cascade Mts. Arrowhead-shaped leaf blades up to 25 cm long and up to 25 cm wide. Inflorescence often a simple raceme.