| Giant Size Hostas | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Macazoo' | Dark-Green | | - | Unknown | - | - | Unknown | --NR-- |
| 'Maddren' | Blue/Green | | - | Hybrid | Pale-Lavender | June into July | Gilligan, Madelon | .2012 |
| 'Mammoth Ears' | Blue/Green | | - | Hybrid | - | June into July | Kruer, George | .2009 |
| 'Mammoth Halo' | Blue/Green | | - | Nat-Sport | Near-White | June into July | Aden, Paul | --NR-- |
| 'Mandelbrot Set' | Light-Green | | - | Hybrid | - | June | Nyikos, Frank | .2011 |
| 'Manfred's Delight' | Light-Green | | - | Unknown | Near-White | June | Mondt, Manfred | --NR-- |
| 'Maple Grove' | Blue/Green | | - | Unknown | - | - | Jernigan, Bettie | --NR-- |
| 'Mary Lou' | Blue/Green | | - | Hybrid | Pale-Lavender | July | Banyai, Pauline | .1986 |
| 'Master Class' | Blue/Green | | - | Hybrid | Pale-Lavender | June into July | Gilligan, Madelon | .2012 |
| 'Memphis Blue' | Blue/Green | | - | Hybrid | - | - | Petryszyn, Olga | --NR-- |
| 'Merry-go-round' | Med-Green | | - | Hybrid | - | - | Elslager, Ed | .1999 |
| 'Metropolis' | Med-Green | | - | Hybrid | Near-White | July into August | Johnson, Greg | .2004 |
| 'Michael T. Rozanski' | Blue/Green | | - | Hybrid | Near-White | June into July | Chamberlain, Steve | .2004 |
| 'Midnight Dream' | Blue/Green | | - | Unknown | - | - | Hackbarth, Robert | .2015 |
| 'Midnight Hour' | Blue/Green | | - | Unknown | Pale-Lavender | June | Ward, Dr Dick & Jane | .2009 |
| 'Midwest Majesty' | Yellow | | - | Nat-Sport | Med-Lavender | July | Minks, Eldren | .1983 |
| 'Mikado' | Dark-Green | | - | Hybrid | Pale-Lavender | - | Aden, Paul | .1982 |
| 'Mike' | Blue/Green | | - | Unknown | - | June into July | Webster, B. | .2010 |
| 'Millennium' | Blue/Green | | - | Hybrid | Pale-Lavender | June into July | Wilkins, Dr Jim & Jill | .1995 |
| 'Minke' | Blue/Green | Marginal | Yellow | Unknown | Pale-Lavender | July into August | Molter Nurseries | --NR-- |
| 'Mira' | Blue/Green | | - | Nat-Sport | Pale-Lavender | June into July | Maekawa, Dr Fumio & AHS | .2002 .2018 |
| 'Miss Lucy' | Blue/Green | | - | Unknown | Near-White | June into July | Simpers, Lucille | --NR-- |
| 'Miss Tokyo' | Med-Green | Marginal | White | Hybrid | Pale-Lavender | June | Hansen, Hans | .2004 |
| 'Mississippi Delta' | Blue/Green | | - | Hybrid | Pale-Lavender | June into July | Petryszyn, Olga | .1998 |
| 'Mississippi Gold' | Yellow | | - | Hybrid | Pale-Lavender | July into August | Simmering, Ron | .2003 |
| 'Mississippi Mud' | Blue/Green | | - | Hybrid | Pale-Lavender | July into August | Simmering, Ron | .2000 |
| 'Misty Regal' | Med-Green | Medial | Yellow | Nat-Sport | Med-Lavender | July | Stratton, John & Elizabeth | .1996 |
| 'Molly Morris' | Yellow | | - | Hybrid | - | June into July | Ward, Dr Dick & Jane | .2014 |
| 'Monitor' | Dark-Green | | - | Unknown | - | July | Moldovan, Steve & Walek, Kevin | .2009 |
| 'Monster Babe' | Blue/Green | | - | Hybrid | Pale-Lavender | - | Minks, Eldren & Malloy, Alex | .2000 |
| 'Montreal Blue Ice Storm' | Blue/Green | | - | Hybrid | Pale-Lavender | June into July | Wade, Van | .2007 |
| 'More Elegant' | Blue/Green | | - | Nat-Sport | Near-White | June | Stadden, Josh | .2001 |
| 'Mount Fuji' | Med-Green | | - | Hybrid | Light-Purple | July | Wilkins, Dr Jim | .1989 |
| 'Mount Kip' | Blue/Green | | - | Unknown | Light-Purple | July | Simpers, Lucille | --NR-- |
| 'Mountain of Love' | Blue/Green | | - | Unknown | - | - | Ziarek, Ken | --NR-- |
| 'Mountain Pride' | Med-Green | | - | Unknown | - | July into August | Benedict, Dr R. (Herb) & Dorothy & Kuenster, Rod | .2010 |
| 'Mr. Big' | Dark-Green | | - | Unknown | Near-White | July | Purtymun, Charles & Ruh, Peter | .2010 |
| 'Mumsie' | Med-Green | | - | Unknown | Pale-Lavender | July into August | Hiselman, Paula & Krul, Nancy | .1999 |
| 'My Man Mark' | Med-Green | | - | Hybrid | - | - | Schmidt, Bevie | .2009 |
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