Key to the species of Ulva
| 1 | Plants reticulate, netlike nature obscuring blade, mostly unattached entangled with other algae | U. reticulata |
| 1 | Plants not reticulate, clearly blade like, mostly attached | 2 |
| 2 | Individual plants with conspicuous narrow segments | 3 |
| 2 | Individual plants with blades broad, rounded | U. expansa |
| 3 | Basally broadened, but upper portions divided deeply into many ribbon like segments; margins smooth, often undulate | U. fasciata |
| 3 | Basally narrowing to a stipe up to 5 mm long, frond narrow, attenuate blades rarely divided, with strongly ruffled margins | U. taeniata |