| Iberis (many) |
Candytuft |
 |
| Iberis pruitii candolleana group |
Candytuft |
 |
| Iberis umbellata |
Candytuft |
 |
| Illicium anisatum |
Chinese Anise |
 |
| Impatiens (many) |
Busy Lizzie |
|
| Impatiens glandulifera |
Policeman's Helmet |
|
| Impatiens x walleriana |
Busy Lizzie |
|
| Incarvillea (many) |
hardy Gloxinia |
|
| Indigofera (many) |
Indigo |
|
| Indigofera gerardiana |
Himalayan Indigo |
|
| Indigofera hebepetala |
Indigo |
|
| Indigofera heterantha |
Himalayan Indigo |
|
| Indigofera potaninii |
Potanin Indigo |
 |
| Inula conyza |
Ploughman's Spikenard |
|
| Iochroma australis |
Blue Angel Trumpet |
|
| Ipomoea (many) |
Morning Glory |
|
| Ipomoea lobata |
Spanish Flag |
|
| Ipomoea pes-caprae |
Beach Morning Glory |
|
| Ipomoea sloteri |
Morning Glory |
|
| Ipomoea tricolor |
Morning Glory |
|
| Ipomoea violacea |
Morning Glory |
|
| Iris (many) |
Iris |
|
| Iris (many) |
Iris |
|
| Iris decora |
Nepal Iris |
|
| Iris foetidissima |
Stinking Gladwyn |
 |
| Iris innominata |
Golden Iris |
|
| Iris pseudacorus |
Yellow Flag |
|
| Iris sibirica |
Siberian Iris |
|
| Iris sintenisii |
German Iris |
|
| Isoplexis canariensis |
Tenerife Shrub Foxglove |
|
| Isoplexis isabellina |
Canary Island Foxglove |
|
| Isoplexis sceptrum |
Giant Madeira Foxglove |
|
| Isotoma |
Blue Star Creeper, Rock Isotome |
|
| Ixia |
Corn Lily |
|
| Ixiolirion |
Siberian Lily |
|
| Ixora coccinea |
Flame of the Woods, Jungle Geranium |
|
