| Ximenesia foetida (Cav.) Spreng., 1826 |
| Ximenesia hispida Kunth, 1820 |
| Ximenesia microptera DC., 1836 |
| Xylorhiza Nutt., 1841 |
| Xylorhiza frutescens (S. Watson) Greene, 1896 |
| Xylorhiza orcuttii (Vasey & Rose) Greene, 1896 |
| Xylorhiza wrightii (A. Gray) Greene, 1896 |
| Xylothamia G.L. Nesom, 1990 |
| Xylothamia diffusa (Benth.) G.L. Nesom, 1990 |
| Xylothamia johnstonii G.L. Nesom, 1990 |
| Xylothamia palmeri (A. Gray) G.L. Nesom, 1990 |
| Xylothamia parrasana (S.F. Blake) G.L. Nesom, 1990 |
| Xylothamia pseudobaccharis (S.F. Blake) G.L. Nesom, 1990 |
| Xylothamia purpusii (Brandegee) G.L. Nesom, 1990 |
| Xylothamia riskindii (B.L. Turner & G. Langford) G.L. Nesom, 1990 |
| Xylothamia triantha (S.F. Blake) G.L. Nesom, 1990 |
| Xylothamia truncata G.L. Nesom, 1992 |
| Xylovirgata Urbatsch & R.P. Roberts, 2004 |
| Xylovirgata pseudobaccharis (S.F. Blake) Urbatsch & R.P. Roberts, 2004 |
| Youngia Cass., 1831 |