| Gretheria Duno & Torke, 2022 |
| Gretheria campylacantha (L. Rico & M. Sousa) Duno & Torke, 2022 |
| Gretheria sonorae (S. Watson) Duno & Torke, 2022 |
| Grimaldia Schrank, 1805 |
| Grimaldia absus (L.) Link, 1831 |
| Grimaldia colombiana Britton & Rose ex Britton & Killip, 1936 |
| Grimaldia deamii Britton & Rose, 1930 |
| Grimaldia enneandra (Brandegee) Britton & Rose, 1930 |
| Grimaldia opifera Schrank, 1805 |
| Grimaldia punctulata (Hook. & Arn.) Britton & Rose, 1930 |
| Grimaldia standleyi Britton & Rose, 1930 |
| Grimaldia viscosa (Kunth) Britton & Rose ex Britton & Killip, 1936 |
| Grona Lour., 1790 |
| Grona adscendens (Sw.) Ohashi & K. Ohashi, 2018 |
| Grona barbata (L.) Ohashi & K. Ohashi, 2018 |
| Grona triflora (L.) H. Ohashi & K. Ohashi, 2018 |
| Guilandina L., 1753 |
| Guilandina bonduc L., 1753 |
| Guilandina bonducella L., 1753 |
| Guinetia L. Rico & M. Sousa, 1999 |