M
- Macleaya cordata (I)
- Maclura pomifera (N)
- Magnolia acuminata (N)
- Magnolia fraseri (N)
- Magnolia macrophylla (N)
- Magnolia × soulangeana (I)
- Magnolia stellata (I)
- Magnolia tripetala (N)
- Mahonia aquifolium (N)
- Maianthemum canadense (N)
- Maianthemum racemosum ssp. racemosum (N)
- Maianthemum stellatum (N)
- Maianthemum trifolium (N)
- Malaxis unifolia (N)
- Malus angustifolia var. angustifolia (N)
- Malus baccata (I)
- Malus coronaria (N)
- Malus floribunda (I)
- Malus ioensis var. ioensis (N)
- Malus × platycarpa (N)
- Malus pumila (I)
- Malus toringo (I)
- Malus zumi (I)
- Malva alcea (I)
- Malva moschata (I)
- Malva neglecta (I)
- Malva pusilla (I)
- Malva sylvestris (I)
- Malva verticillata (I)
- Manfreda virginica (N)
- Marrubium vulgare (I)
- Marsilea quadrifolia (I)
- Marsilea quadrifolia (N)
- Matelea obliqua (N)
- Matricaria discoidea (I)
- Matricaria recutita (I)
- Matteuccia struthiopteris (N)
- Mazus pumilus (I)
- Medeola virginiana (N)
- Medicago lupulina (I)
- Medicago polymorpha (I)
- Medicago sativa ssp. falcata (I)
- Medicago sativa ssp. sativa (I)
- Meehania cordata (N)
- Melampyrum lineare var. latifolium (N)
- Melampyrum lineare var. lineare (N)
- Melica nitens (N)
- Melilotus altissimus (I)
- Melilotus officinalis (I)
- Melissa officinalis (I)
- Menispermum canadense (N)
- Mentha aquatica (I)
- Mentha arvensis (N)
- Mentha × gracilis (I)
- Mentha × piperita (N)
- Mentha × rotundifolia (I)
- Mentha spicata (I)
- Mentha suaveolens (I)
- Mentha × villosa (I)
- Menyanthes trifoliata (N)
- Mercurialis annua (I)
- Mertensia virginica (N)
- Microstegium vimineum (I)
- Microthlaspi perfoliatum (I)
- Mikania scandens (N)
- Milium effusum var. cisatlanticum (N)
- Mimulus alatus (N)
- Mimulus ringens var. ringens (N)
- Minuartia michauxii var. michauxii (N)
- Minuartia patula (N)
- Mirabilis albida (N)
- Mirabilis hirsuta (N)
- Mirabilis jalapa (I)
- Mirabilis nyctaginea (N)
- Miscanthus sinensis (I)
- Misopates orontium (I)
- Mitchella repens (N)
- Mitella diphylla (N)
- Moehringia lateriflora (N)
- Moehringia trinervia (I)
- Mollugo verticillata (N)
- Monarda clinopodia (N)
- Monarda didyma (N)
- Monarda fistulosa ssp. fistulosa var. fistulosa (N)
- Monarda fistulosa ssp. fistulosa var. mollis (N)
- Monarda fistulosa ssp. fistulosa (N)
- Monarda media (N)
- Monarda punctata ssp. punctata var. villicaulis (N)
- Monarda punctata ssp. punctata (N)
- Moneses uniflora (N)
- Monolepis nuttalliana (N)
- Monotropa hypopithys (N)
- Monotropa uniflora (N)
- Morella pensylvanica (N)
- Morus alba (I)
- Morus nigra (I)
- Morus rubra var. rubra (N)
- Muhlenbergia asperifolia (N)
- Muhlenbergia capillaris (N)
- Muhlenbergia × curtisetosa (N)
- Muhlenbergia cuspidata (N)
- Muhlenbergia frondosa (N)
- Muhlenbergia glomerata (N)
- Muhlenbergia mexicana (N)
- Muhlenbergia schreberi (N)
- Muhlenbergia sobolifera (N)
- Muhlenbergia sylvatica (N)
- Muhlenbergia tenuiflora (N)
- Muscari armeniacum (I)
- Muscari botryoides (I)
- Muscari comosum (I)
- Muscari neglectum (I)
- Myagrum perfoliatum (I)
- Myosotis arvensis (I)
- Myosotis discolor (I)
- Myosotis laxa (N)
- Myosotis macrosperma (N)
- Myosotis scorpioides (I)
- Myosotis stricta (I)
- Myosotis sylvatica (I)
- Myosotis verna (N)
- Myosoton aquaticum (I)
- Myosurus minimus (N)
- Myriophyllum aquaticum (I)
- Myriophyllum heterophyllum (N)
- Myriophyllum humile (N)
- Myriophyllum pinnatum (N)
- Myriophyllum sibiricum (N)
- Myriophyllum spicatum (I)
- Myriophyllum verticillatum (N)
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