| Author | Michaux | |
| Distribution | Scattered over the northern half of the state, in all three provinces. As it is an aquatic submerged species, it is certainly under-collected.
The species occurs across most of Canada and the US, though is mainly found in the northern and central regions, south mostly only to SC, Panhandle FL, MO, and CA.
| |
| Abundance | Uncommon to rare in the northern parts of the state, and very rare to absent in the southern half. This is a Watch List species. The NCNHP's State Rank of S1? is clearly too conservative, and the editors suggest S2? | |
| Habitat | This is a species of slow moving waters, in lakes, ponds, and creeks/rivers. |
| Phenology | Flowers and fruits from July to September. | |
| Identification | This is a mainly submerged aquatic plant, in long strands, often growing in masses. The stems are branched, with leaves in whorls of 3, each leaf elliptic to oblong, averaging about 1/2-inch long and 1/8-inch wide, with an obtuse (rounded) tip. The staminate flowers are at the ends of branches, each flower about 1/3-inch across, with 6 segments, and white in color, on a quite long and very slender stalk. You may need to look at photos or drawings to better note the flower structure. E. nuttallii is similar but has linear whorled leaves, with acute tips; however, they can occur in the same or at least in similar places. Do not confuse these two native species with the obnoxious exotic weed Hydrilla verticillata. That species has leaves typically in whorls of 4 or more leaves, and the leaves are toothed with sharp teeth on the margins. | |
| Taxonomic Comments | A very few older references named the species as Anacharis canadensis.
| |
| Other Common Name(s) | Common Waterweed, American Waterweed, Canadian Pondweed | |
| State Rank | S1? [S2?] | |
| Global Rank | G5 | |
| State Status | W7 [W1] | |
| US Status | | |
| USACE-agcp | OBL link |
| USACE-emp | OBL link |
