I
- Iberis umbellata (I)
- Ilex crenata (I)
- Ilex mucronata (N)
- Ilex opaca var. opaca (N)
- Ilex verticillata (N)
- Impatiens balsamina (I)
- Impatiens capensis (N)
- Impatiens pallida (N)
- Inula helenium (I)
- Iodanthus pinnatifidus (N)
- Ionactis linariifolius (N)
- Ipomoea coccinea (I)
- Ipomoea hederacea (I)
- Ipomoea lacunosa (N)
- Ipomoea pandurata (N)
- Ipomoea purpurea (I)
- Ipomopsis rubra (N)
- Iris brevicaulis (N)
- Iris cristata (N)
- Iris fulva (N)
- Iris germanica (I)
- Iris pseudacorus (I)
- Iris verna var. smalliana (N)
- Iris versicolor (N)
- Iris virginica var. shrevei (N)
- Isoetes engelmannii (N)
- Isoetes tenella (N)
- Isotria medeoloides (N)
- Isotria verticillata (N)
- Iva annua var. annua (N)
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