U
- Ulmus americana (N)
- Ulmus procera (I)
- Ulmus pumila (I)
- Ulmus rubra (N)
- Ulmus thomasii (N)
- Urtica chamaedryoides (N)
- Urtica dioica ssp. gracilis (N)
- Urtica dioica ssp. dioica (I)
- Utricularia cornuta (N)
- Utricularia geminiscapa (N)
- Utricularia gibba (N)
- Utricularia intermedia (N)
- Utricularia macrorhiza (N)
- Utricularia minor (N)
- Uvularia grandiflora (N)
- Uvularia perfoliata (N)
- Uvularia sessilifolia (N)
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