“Exotic” is a botanical and horticultural term that refers to plants that are non-native.
“Exotic: not native to a particular area, habitat, or soil type; introduced; e.g. tropical plants grown in temperate climates.” (from A Botanist’s Vocabulary, Timber Press, 2016)
“Exotic species: An introduced, non-native species” (from Oxford Concise Dictionary of Botany 1992, Oxford University Press)
“exotic: Of foreign origin or character; introduced from a foreign country or a different region. An exotic plant is one not native to the place where it is growing, such as Japanese honeysuckle, which has naturalized in the northeastern states, or eucalyptus trees, which have naturalized on the west coast.” (from National Gardening Association Dictionary of Horticulture, copyright 1994, published in Penguin Books 1996.)
The plants of the genus Hemerocallis may be referred to as exotic in North America, but not in Asia where they are native. (This term could also apply to the daylily leafminer, daylily gall midge, and daylily rust, since the term is also used for introduced pests.)