| Galphimia glauca | Thryallis glauca |
| Garcinia madruno | Rheedia madruno |
| Garcinia magnifolia | Rheedia magnifolia |
| Gardenia jasminoides | Gardenia grandiflora, Gardenia radicans, Gardenia augusta, Gardenia schlechteri, Gardenia florida |
| Gardenia taitensis | Gardenia tahitensis, Randia tahitensis |
| Ginkgo biloba | Ginkgo macrophylla, Salisburia biloba |
| Gladiolus scullyi | Gladiolus venustus |
| Glandularia canadensis | Glandularia aubletia, Buchnera canadensis, Verbena canadensis |
| Gliricidia sepium | Gliricidia maculata |
| Gloriosa rothschildiana | Gloriosa superba var. rothschildiana |
| Glycyrrhiza glabra | Glycyrrhiza glandulifera, Glycyrrhiza officinalis, Glycyrrhiza hirsuta, Liquiritia officinalis |
| Gmelina asiatica | Gmelina parvifolia |
| Gompholobium confertum | Burtonia conferta |
| Gonatopus boivinii | Zamioculcas boivinii |
| Gordonia lasianthus | Gordonia pyramidalis, Hypericum lasianthus |
| Gossypium hirsutum | Gossypium mexicanum, Gossypium religiosum, Gossypium latifolium, Gossypium taitense, Gossypium punctatum, Gossypium marie-galante |
| Grahamia coahuilensis | Talinum coahuilense, Talinaria coahuilensis |
| Grewia avellana | Grewia guazumifolia |
| Grewia flava | Grewia cana, Grewia hermannioides |
| Grewia hexamita | Grewia messinica, Grewia schweickerdtii |
| Grewia monticola | Grewia obliqua |
| Grewia occidentalis | Grewia chirindae, Grewia microphylla, Grewia rudatisii |
| Guaiacum angustifolium | Porlieria angustifolia |
| Guazuma ulmifolia | Guazuma tomentosa, Guazuma polybotrya, Theobroma guazuma, Guazuma bubroma, Theobroma foliis serratis, Diuroglossum rufescens |
| Gymnocladus dioica | Gymnocladus canadensis |
| Gynostemma hederifolium | Sicyos hederifolia |
| Gyrocarpus americanus | Gyrocarpus jacquinii, Gyrocarpus asiaticus |