| Ageratina gentryana B.L. Turner, 1987 |
| Ageratina glabrata (Kunth) R.M. King & H. Rob., 1970 |
| Ageratina glauca (Sch. Bip. ex Klatt) R.M. King & H. Rob., 1970 |
| Ageratina glischra (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina gonzalezorum B.L. Turner, 1985 |
| Ageratina grandidentata (DC.) R.M. King & H. Rob., 1970 |
| Ageratina grandifolia (Regel) R.M. King & H. Rob., 1986 |
| Ageratina grashoffii B.L. Turner, 1986 |
| Ageratina gypsophila B.L. Turner, 1985 |
| Ageratina halbertiana (McVaugh) R.M. King & H. Rob., 1972 |
| Ageratina hasegawana B.L. Turner, 2010 |
| Ageratina havanensis (Kunth) R.M. King & H. Rob., 1970 |
| Ageratina hebes (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina hederifolia (A. Gray) R.M. King & H. Rob., 1970 |
| Ageratina helenae R.M. King & H. Rob., 1972 |
| Ageratina henzium B.L. Turner, 1990 |
| Ageratina herbacea (A. Gray) R.M. King & H. Rob., 1970 |
| Ageratina hernandezii B.L. Turner, 1987 |
| Ageratina herrerae R.M. King & H. Rob., 1990 |
| Ageratina hidalgensis (H. Rob.) R.M. King & H. Rob., 1970 |