| Common name | Botanical name |
| 1. Iboza | Iboza riparia |
| 2. Iceland Moss | Cetraria islandica |
| 3. Ichnocarpus | Ichnocarpus frutiscens |
| 4. Ignatius Beans | Strychnos ignatii |
| 5. Immortelle | Xeranthemum annuum |
| 6. Impatiens | Impatiens wallerana |
| 7. Incense-cedar | Librocedrus decurrens |
| 8. Indian elm, Kanju | Holoptelea integrifolia |
| 9. Indian pipe | Monotropa |
| 10. Indicus Cocculus | Anamirta paniculata |
| 11. Indigo | Indigofera constricta Indigofera tinctoria |
| 12. Indigo, Wild | Baptisia tinctoria |
| 13. Inga | Inga cynometroides |
| 14. Ipecacuanha | Cephaelis ipecacuanha |
| 15. Ipecacuanha, Black | Psychotria emetica |
| 16. Ipecacuanha, East Indian | Cryptocarpus spiralis |
| 17. Ipecacuanha, White | Euphorbia ipecacuanha Ionidium ipecacuanha |
| 18. Ipsea | Ipsea malabarica |
| 19. Iris, Florentine | Iris x germanica var. florentina |
| 20. Iris, Japanese | Iris ensata |
| 21. Iris, Oregon | Iris tenax |
| 22. Iris, Roof, Japanese | Iris tectorum |
| 23. Iris, Siberian | Iris sibirica |
| 24. Iris, Spanish | Iris xiphium |
| 25. Iris, Variegated | Iris variegata |
| 26. Iris, Wild | Iris shrevei |
| 27. Iris, Winter | Iris unguicularis |
| 28. Irish Heath | Daboecia cantabrica |
| 29. Irish Moss | Chondrus crispus |
| 30. Iron Cross | Begonia masoniana |
| 31. Ironbark, Red | Eucalyptus sideroxylon |
| 32. Ironbark, White | Eucalyptus leucoxylon |
| 33. Ironweed | Vernonia fasciculata Vernonia noveboracensis |
| 34. Ironweed, Little/ Ash coloured Fleabane | Vernonia cinerea |
| 35. Isachne | Isachne fischeri |
| 36. Island Alum Root | Heuchera maxima |
| 37. Isonandra | Isonandra villosa |
| 38. Ispaghula | Plantago amplexicaulis |
| 39. Itch-bulb | Drimia ciliaris |
| 40. Ithi | Ficus gibosa |
| 41. Iva | Achillea moschata Iva xanthifolia |
| 42. Ivy, Common | Hedera helix |
| 43. Ivy-Leafed Cyclamen | Cyclamen hederaefolium |
| 44. Ivy-leaved Toadflax | Cymbalaria muralis Linaria cymbalaria |
| 45. Ixora | Ixora coccinea |