| Common Name | Latin Name |
|---|---|
| Mandrake | see Mayapple |
| Marestail | see Horseweed |
| Marijuana | Cannabis sativa |
| Marlahan mustard | see Dyers Woad |
| Marsh Dayflower | Murdannia keisak |
| Marsh Pennywort | Hydrocotyle umbellata |
| Marshelder | Iva annua |
| Mary'S Grass | see Japanese Stiltgrass |
| Mayapple | Podophyllum peltatum |
| Maypop Passionflower | Passiflora incarnata |
| Mayweed | see Mayweed Chamomile |
| Mayweed Chamomile | Anthemis cotula |
| Meadow Foxtail | Alopecurus pratensis |
| Meadow Garlic | see Wild Onion |
| Mexican Sandbur | see Puncturevine |
| Microstegium | see Japanese Stiltgrass |
| Midwestern Arrowhead | Sagittaria brevirostra |
| Milfoil | see Common Yarrow |
| Mimosa | Albizia julibrissin |
| Missouri Fuzzy Bean | Strophostyles helvula missouriensis |
| Mockernut Hickory | see Hickory |
| Mole Plant | see Caper Spurge |
| Morrow's Bush-Honeysuckle | Lonicera morrowii |
| Moss Pink | see Creeping Phlox |
| Moth Mullein | Verbascum blattaria |
| Mouse-ear Cress | Arabidopsis thaliana |
| Mouseear Chickweed | Cerastium vulgatum |
| Mouseear Hawkweed | Hieracium pilosella |
| Mousetail | Myosurus minimus |
| Mugwort | Artemisia vulgaris |
| Mulberry Weed | Fatoua villosa |
| Mullein | see Common Mullein |
| Multiflora Rose | Rosa multiflora |
| Musk Thistle | Carduus nutans |
| Musk-grass | see Chara |
