Plants — I
- Iberis Candytuft
- Ichnocarpus frutescens
- Idesia polycarpa Idesia
- Ilex Holly
- Ilex aquifolium English holly
- Ilex guayusa
- Ilex paraguariensis Yerba mate
- Ilex vomitoria Yaupon Holly
- Illicium Anisetree
- Illicium henryi Henry's Anise
- Illicium verum Chinese star-anise
- Impatiens balsamina Balsam
- Impatiens pallida
- Indigofera pseudotinctoria Dwarf false-indigo
- Indigofera tinctoria Indian indigo
- Inula helenium Elecampane
- Ipomoea Morning-glory
- Ipomoea aquatica water spinach
- Ipomoea batatas sweet potato
- Ipomoea cairica Cairo Morning Glory
- Ipomoea coptica alamovine
- Ipomoea mauritiana Forest Morning Glory
- Ipomoea muricata
- Ipomoea nil Annua morning glory
- Ipomoea pes-caprae
- Ipomoea pes-tigridis Morningglory
- Ipomoea purga Veracruz jalap
- Ipomoea purpurea Annual Morning Glory
- Ipomoea sagittifolia
- Ipomoea tricolor Garden Morning Glory
- Iris domestica Blackberry Lily
- Iris × germanica Iris x germanica
- Iris haussknechtii Iris kerneriana
- Iris humilis
- Iris leptophylla thin-leaf iris
- Iris mesopotamica Mesopotamian Iris
- Iris missouriensis
- Iris narbutii
- Iris palaestina
- Iris pallida subsp. illyrica Iris illyrica
- Iris pseudacorus Flag Iris
- Iris rossii Long-tail iris
- Iris ruthenica
- Iris sanguinea Blood Iris
- Iris setosa Alaska iris
- Iris sibirica German Iris
- Iris songarica
- Iris suaveolens
- Iris tenuifolia slender-leaf iris
- Iris tigridia thick-root iris
- Iris uniflora
- Irvingia malayana
- Isatis tinctoria Dyer's Woad
- Isodon japonicus Bangahpul (East Asian soup-mint)
- Isodon rubescens Blushred Teacost
- Isotrema austroyunnanense
- Isotrema championii
- Isotrema cucurbitoides
- Isotrema fangchi
- Isotrema hainanense
- Isotrema howii
- Isotrema kwangsiense
- Isotrema manshuriense
- Isotrema scytophyllum
- Isotrema transsectum
- Isotrema versicolor
- Ixeris chinensis Yellow bristle-hair ixeris