Northern Prairie Wildlife Research Center
Reference: Fernald, M. L. 1922. Notes on Sparganium. Rhodora 24:26-34.
| Lead | Characteristic | Go To |
| 1 | Stigma 1; achenes fusiform, rounded on the sides; staminate heads usaully 2-5. | Lead 2 |
| 1 | Stigmas 2; achenes obconic to obpyramidal, angled on the sides; staminate heads many. | S. eurycarpum |
| 2 | Achene body (excluding stipe and beak) 3.5-5 mm long at maturity; achene beak (including stigma) 2-4.2 mm long; leaves mostly 3-5(7) mm wide; bracts usually not dilated at the base. | S. chlorocarpum |
| 2 | Achene body (excluding stipe and beak) 2-3.5 mm long at maturity; achene beak (including stigma) 2-3 mm long; leaves mostly (5)6-12 mm wide; bracts usually stongly dilated at the base, with broad, scarious margins. | S. emersum |