| Common Name | Group |
|---|---|
| Xanthocercis madagascariensis | Plants |
| Xanthocercis rabiensis | Plants |
| Xanthophyllum bullatum | Plants |
| Xanthophyllum sulphureum | Plants |
| Xanthosoma eggersii | Plants |
| Xanthosoma weeksii | Plants |
| Xanthostemon glaucus | Plants |
| Xanthostemon oppositifolius | Plants |
| Xanthostemon sulfureus | Plants |
| Xanthostemon verdugonianus | Plants |
| Xenophyllum acerosum | Plants |
| Xenophyllum rigidum | Plants |
| Xenophyllum roseum | Plants |
| Ximenia roigii | Plants |
| Xiphopteris ascensionense | Plants |
| Xolocotzia asperifolia | Plants |
| Xylopia africana | Plants |
| Xylopia amplexicaulis | Plants |
| Xylopia ekmanii | Plants |
| Xylopia elliotii | Plants |
| Xylopia lamarckii | Plants |
| Xylopia latipetala | Plants |
| Xylopia longifolia | Plants |
| Xylopia pierrei | Plants |
| Xylopia richardii | Plants |
| Xylopia talbotii | Plants |
| Xyris andina | Plants |
| Common Name | Group |
|---|---|
| Yadon's Piperia | Plants |
| Yakushima White Pine | Plants |
| Yellow Larkspur | Plants |
| Yellow Sterculia | Plants |
| Yreka Phlox | Plants |