- Nabalus albus
- Najas marina
- Napaea dioica
- Narcissus bulbocodium
- Narcissus jonquilla
- Narcissus poeticus
- Narcissus pseudonarcissus
- Narcissus tazetta
- Narthecium ossifragum
- Nauclea orientalis
- Nemophila aphylla
- Neotinea ustulata
- Neottia cordata
- Neottia nidus-avis
- Neottia ovata
- Nepenthes distillatoria
- Nerine sarniensis
- Nerium oleander
- Nicandra physalodes
- Nicotiana glutinosa
- Nicotiana rustica
- Nicotiana tabacum
- Nigella damascena
- Nigella sativa
- Niphidium crassifolium
- Nothoscordum bivalve
- Nuttallanthus canadensis
- Nyctanthes arbor-tristis
- Nymphaea alba
- Nymphaea lotus
- Nyssa aquatica
Nerium oleander
- Oleander (Nerium oleander)
- Insufficient research to evaluate efficacy.<wiki/List_of_medicinal_plants#cite_note-oleander-167"> Used for muscle cramps, asthma, cancer, and <wiki/AIDS" title="AIDS">AIDS.<wiki/List_of_medicinal_plants#cite_note-168"><wiki/List_of_medicinal_plants#cite_note-oleanderc-169">
- Oleander leaf is poisonous, and can cause fatal heart failure. Symptoms may include nausea, vomiting, colic, appetite loss, dizziness, drowsiness, high potassium levels, dilated pupils, bloody diarrhea, seizures, loss of consciousness, slow or irregular pulse, and heart block.<wiki/List_of_medicinal_plants#cite_note-oleanderc-169"> Oleander seeds are also toxic, as is the rest of the plant, sap, twigs, roots, etc.<wiki/List_of_medicinal_plants#cite_note-oleander-167">