| Author | (Planchon) St. John | |
| Distribution | Present over much of the northern and central parts of the state, in all three provinces. As with E. canadensis, records are lacking from the southern parts of the state, perhaps owing to collection effort.
This is a widespread but mostly Northern species, ranging from Canada south to NC, AR, and CA, rarely to SC and MS.
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| Abundance | Infrequent to locally fairly common in the northern half of the Coastal Plain and the northern half of the Mountains; rare in the northern Piedmont. Very rare to absent in the southern parts of the state. This is a Watch List species, as designated by the NCNHP; however, with collections from 17 counties, it probably does not need to be on such a list. The website editors suggest a State Rank of S3?. | |
| Habitat | This is a species of calm to slowly moving waters, of ponds, lakes, and rivers/creeks. |
| Phenology | Flowers and fruits from July to September. | |
| Identification | This is a mainly submerged aquatic plant, similar in characters to E. canadensis, occurring in long, branched "strings". This species has its whorled leaves (in 3's) linear and with sharp tips, about 1/3-inch long but barely 1/20-inch wide; they are often twisted and/or curled. It also has the staminate flowers in axillary spathes, which after anthesis break free from the plant and float on the water nearby. E. canadensis has wider leaves that are rounded (obtuse) at the tip, and the staminate flowers are on long stalks from the tips of branches. The exotic Hydrilla verticillata, a noxious weed, is similar but has its leaves in whorls of 4 or more, and the leaves have sharp teeth along the margins. | |
| Taxonomic Comments | A few old references named the species as Anacharis nuttallii.
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| Other Common Name(s) | Western Waterweed | |
| State Rank | S2? [S3?] | |
| Global Rank | G5 | |
| State Status | W7 [W1] | |
| US Status | | |
| USACE-agcp | OBL link |
| USACE-emp | OBL link |
