| Author | (A. Braun ex Engelmann) Magnus | |
| Distribution | Scattered over the Mountains and Piedmont, but only at a few localities in the northern Coastal Plain. Certainly under-collected, as it is a very small, submerged, aquatic species.
This is an Eastern species, ranging from N.S. to MN south to SC and MS, but with relatively few collections south of MD and MO.
| |
| Abundance | Infrequent in the Mountains and at least the northern and central Piedmont; apparently very rare in the Coastal Plain. This is a Watch List species, but its State Rank might best be S3? instead of S2. | |
| Habitat | This is a species of pools, ponds, and lakes; rarely in streams where the flow is sluggish. | |
| Phenology | Flowers and fruits from July to October. | |
| Identification | This is a submerged plant, with strongly filamentous (needle-like) leaves. The stem grows to 8 inches long and is branched, with opposite leaves. These leaves are about 3/4-inch long and extremely narrow, but with teeth scattered along the margins; and the leaf base is widened and with teeth along the front face. Flowers are tiny and not of note for identification. This species has the base of the leaf squared to truncate; N. guadalupensis has the leaf base rounded and with 20 or more extremely tiny serrations along a leaf margin. The non-native N. minor has a similar leaf base, but its leaves are stiff and recurved, as opposed to slender, flexible, and rather straight in N. gracillima. | |
| Taxonomic Comments | None
| |
| Other Common Name(s) | Slender Naiad, Bushy Naiad, Thread-leaf Naiad | |
| State Rank | S2 [S3?] | |
| Global Rank | G5? | |
| State Status | W7 [W1] | |
| US Status | | |
| USACE-agcp | OBL link |
| USACE-emp | OBL link |
