| Cultivar Name | Plant Size | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Madame Butterfly' (Gowen) | Medium | Dark-Green | Medial | Yellow | Hybrid | Pale-Lavender | July | Gowen, Hideko | .1999 |
| 'Magic Island' | Small | Yellow | Marginal | Blue-Green | Sport | Med-Lavender | July into August | Heemskerk, Gerardus | .2011 |
| 'Magic Mountain' | Large | Blue/Green | - | - | Hybrid | Pale-Lavender | June into July | Ward, Dr Dick & Ward, Jane | .2003 |
| 'Magnificent Obsession' | Large | Med-Green | Marginal | White | Hybrid | Pale-Lavender | July | Elslager, Ed | .1999 |
| 'Main Event' | Medium | Yellow | - | - | Hybrid | Near-White | June into July | Ward, Dr Dick & Ward, Jane | .2015 |
| 'Majestic' | Large | Dark-Green | Marginal | Yellow | Hybrid | Pale-Lavender | July into August | Goodwin, Randy | .2005 |
| 'Maltese Falcon' | Medium | Dark-Green | | | Unknown | | | Malloy, Alex | --NR-- |
| 'Mama Mia' | Medium | Med-Green | Marginal | Creamy White | Unknown | Pale-Lavender | July | Benedict, Dr Ralph (Herb) & Walek, Kevin | .2009 |
| 'Man of Steel' | Large | Blue/Green | Marginal | Yellow | Nat-Sport | Pale-Lavender | June into July | Van Eechaute, Danny | --NR-- |
| 'Man on the Moon' | - | Blue/Green | Streaked | White | TC Sport | - | - | Beilstein, Doug & Zilis, Mark | .2009 |
| 'Manchester by the Sea' | - | - | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Mandrake the Magician' | Small | Med-Green | Streaked | White | Sport | Light-Purple | July | Malloy, Alex | --NR-- |
| 'Manhattan' | Medium | Dark-Green | - | - | Hybrid | Light-Purple | July | Brincka, Wm & Petryszyn, Olga | .1994 |
| 'Marie Curie' | Large | Med-Green | - | - | Unknown | Pale-Lavender | July | Hensen, Karel & Ruh, Peter | .2002 |
| 'Marilyn' | Medium | Yellow | - | - | Hybrid | Pale-Lavender | June into July | Zilis, Mark | .1990 |
| 'Marilyn Monroe' | Medium | Yellow | - | - | Hybrid | Light-Purple | September | Hawes, James & Ruh, Peter | .2005 |
| 'Mark Anthony' | Large | Med-Green | Medial | Yellow | Hybrid | Pale-Lavender | June into July | Johnson, Greg | .2004 |
| 'Mary-Mary' | Medium | Dark-Green | Marginal | White | Unknown | - | June into July | Schwarz, Jim | .2009 |
| 'Masked Marvel' | Medium | Dark-Green | Medial | White | Sport | Pale-Lavender | July into August | Malloy, Alex | --NR-- |
| 'Mata Hari' | Large | Dark-Green | Medial | White | Sport | Pale-Lavender | July into August | Strandberg, Mark | --NR-- |
| 'Matilda' | Medium | Med-Green | Marginal | White | Hybrid | Pale-Lavender | July into August | Kuenster, Rod | .2007 |
| 'Matrix' | Small | Med-Green | Medial | White | TC Sport | Pale-Lavender | July | Zilis, Mark | .2003 |
| 'McFly' | Medium | Blue/Green | - | - | Hybrid | - | - | Stadden, Josh | --NR-- |
| 'Medicine Man' | Medium | Yellow | Marginal | Blue-Green | Unknown | - | - | Wade, Van | --NR-- |
| 'Mercury Rising' | Medium | Yellow | | - | Unknown | Med-Lavender | July into August | Dye, Kay | .2020 |
| 'Merlin' | Medium | Blue/Green | Marginal | Yellow | Hybrid | Light-Purple | July | Ward, Dr Dick & Ward, Jane | .2003 |
| 'Metropolis' | Giant | Med-Green | - | - | Hybrid | Near-White | July into August | Johnson, Greg | .2004 |
| 'Midnight Express' | Large | Blue/Green | - | - | Hybrid | Pale-Lavender | June into July | Ward, Dr Dick & Ward, Jane | .1996 |
| 'Midnight Sun' | Large | Yellow | - | - | Hybrid | Light-Purple | June | Ward, Dr Dick & Ward, Jane | .1996 |
| 'Midsummer Night's Green' | Large | Dark-Green | - | - | Hybrid | Med-Lavender | July into August | Goodwin, Randy | .2006 |
| 'Mighty Mite' | Small | Med-Green | - | - | Hybrid | Med-Lavender | August to September | Dean, Don | .2004 |
| 'Mighty Mouse' | Small | Blue/Green | Marginal | Yellow | Sport | Light-Purple | July | Walters Gardens | .2006 |
| 'Millennium' | Giant | Blue/Green | - | - | Hybrid | Pale-Lavender | June into July | Wilkins, Dr Jim & Wilkins, Jill | .1995 |
| 'Million Dollar Baby' | Large | Blue/Green | Medial | Yellow | Hybrid | Near-White | July into August | Elslager, Ed | .2005 |
| 'Minnie Mouse' | - | - | - | - | Duplicate | - | - | Duplicate Name | --NR-- |
| 'Moby Dick' | Large | Blue/Green | - | - | Hybrid | Near-White | July into August | Brill, Kirk | .1999 |
| 'Moe' | Small | Dark-Green | Marginal | Yellow | Unknown | - | - | Unknown | --NR-- |
| 'Mogul' | Medium | Dark-Green | - | - | Hybrid | Pale-Lavender | July into August | Savory, Robert | .1988 |
| 'Mommy's Little Monster' | Medium | Blue/Green | - | - | Hybrid | - | - | Stadden, Josh | --NR-- |
| 'Montreal White' | - | - | - | - | Duplicate | - | - | Duplicate Name | --NR-- |
| 'Monty Python' | Medium | Yellow | Streaked | White | TC Sport | Pale-Lavender | July | Zilis, Mark | .2009 |
| 'Moon Struck' | - | - | - | - | Duplicate | - | - | Duplicate Name | --NR-- |
| 'Moonlight Child' | - | - | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Morning Light' | Medium | Med-Green | Medial | White | Sport | Pale-Lavender | July into August | Van Eijk-Bos, Gert & Van Erven, Dirk | .2000 .2016 |
| 'Mostly Ghostly' | Small | Yellow | - | - | Nat-Sport | Pale-Lavender | July | Unknown | --NR-- |
| 'Mother Lode' | Large | Dark-Green | Streaked | Speckles | Hybrid | - | - | Elslager, Ed | .2003 |
| 'Mother of Invention' | Small | Med-Green | Marginal | Yellow | Unknown | - | - | Livingston, Ron | --NR-- |
| 'Moulin Rouge' | Medium | Dark-Green | Medial | White | Sport | Pale-Lavender | July into August | Van Eechaute, Danny | .2010 |
| 'Munchkin' | Medium | Med-Green | - | - | TC Sport | Light-Purple | June into July | Zilis, Mark | .2003 |
| 'Munchkin Fire' | Miniature | Light-Green | - | - | Unknown | Med-Lavender | July | Goodwin, Randy | .2009 |
| 'Munchkin Girl' | Small | Dark-Green | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Munchkin Madness' | Medium | Med-Green | Marginal | White | Unknown | Light-Purple | July | Wade, Van | --NR-- |
| 'My Blue Heaven' | Medium | Blue/Green | - | - | Unknown | Light-Purple | July | Banyai, Pauline & Elslager, Ed | .1997 |
| 'My Fair Lady' | Medium | Blue/Green | Marginal | Yellow | Hybrid | Near-White | June into July | Hansen, Hans | .2021 |
| 'My Gal Sal' | Medium | Yellow | Streaked | White | Sport | - | July into August | Freeman, Franc | .2009 |
| 'Mystery Date' | - | Med-Green | Streaked | White | Unknown | - | - | Malloy, Alex | --NR-- |
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