| Hydrophyllum acerifolium Salisb. | Hydrophyllum canadense L. |
| Hydrophyllum albifrons fendleri (A.Gray) Brand | Hydrophyllum fendleri (A.Gray) A.Heller |
| Hydrophyllum aldea Schult. | Phacelia secunda J.F.Gmel. |
| Hydrophyllum lobatum Stokes | Hydrophyllum canadense L. |
| Hydrophyllum macrophyllum occidentale S.Watson, Botany [Fortieth Parallel] 248 (1871) | Hydrophyllum occidentale (S.Watson) A.Gray |
| Hydrophyllum magellanicum Lam. | Phacelia secunda J.F.Gmel. |
| Hydrophyllum occidentale fendleri A.Gray, Proc. Amer. Acad. Arts 10: 314 (1875) | Hydrophyllum fendleri (A.Gray) A.Heller |
| Hydrophyllum occidentale watsonii A.Gray | Hydrophyllum occidentale (S.Watson) A.Gray |
| Hydrophyllum tenuipes viride Jeps. | Hydrophyllum tenuipes A.Heller |
| Hydrophyllum thompsonii M.Peck, Torreya 28: 55 (1928) | Hydrophyllum capitatum Douglas ex Benth. |
| Hydrophyllum viridulum G.N.Jones | Hydrophyllum tenuipes A.Heller |
| Hydrophyllum watsonii (A.Gray) Rydb. | Hydrophyllum occidentale (S.Watson) A.Gray |