- M. Brunswick & Co. (3)
- Magnuson, Louise (4)
- Manhattan Nursery (1)
- Maple Grove Nurseries (1)
- Marlow Seed Company (2)
- Marshalls Nurseries (NE) (2)
- Mattioli, Pietro Andrea (55)
- McDonald, Susan (2)
- McDowell Ginseng Garden (1)
- McFarland, Terry (7)
- McFarland, Terry L. (1)
- McGreer Brothers (1)
- McKay Nursery Co. (1)
- McLean, J.H. (1)
- Mel L. Webster Company (1)
- Menomonie-Eau Claire Nurseries, Inc. (1)
- Meyer, E.L. (1)
- Michaux, André (2)
- Mills Seed Company (5)
- Minnewaska Nursery (1)
