- Macmillan Nurse (s) - Rose pink. 1996.
- Maestro (s) - Lavender. B.R.Jones/Beane/Cave, 2009.
- Maggie May (s) - Blue flush on cream. W.Thomas, 1978.
- Magic (s) - Salmon pink on cream. Walker, 1986
- Magnificent Mauve (s) - Mauve . Harrod.
- Majesty (s) - White. 1967.
- Mamma Mia - synonym of Erewhon
- Marbled Purple - synonym of The Major
- Margaret(1) (e) - A deep rose EMG sweet pea.
- Margaret(2) (s) - Orange pink. Pettifer, 2004.
- Margaret Fife (s) - Pale lavender blue. Malcolm, 1915.
- Margaret Hastie (s) - Lavender stripe, white ground. Parsons, 2011.
- Margaret Hughson (s) - White, pink flush wings. Chisholm, 2008.
- Margaret Joyce (s) - Mid blue. Robertson, 1996.
- Margaret Sarah (s) - Mid blue. 2004.
- Margot (s) - Cream. pre 1969.
- Marguerite (s) - Lavender. pre 1971.
- Marilyn (e) - A scarlet cerise EMG sweet pea.
- Mariner (e) - A blue Spencer Praecox variety.
- Marion(1) (e) - A cream Cuthbertson Florabunda. Cuthbertson.
- Marion(2) (s) - Lavender, darker veins. Walker, 1983.
- Mark Harrod (s) - Scarlet. Harrod, 2007.
- Marks Tey (s) - Violet/maroon bicolour. 1913.
- Marmalade Sky (s) - Orange-red stripe. 1997.
- Maroon Magic (s) - Maroon. 1993.
- Mars (s) - Red stripe. 1996.
- Martha Lane Fox (s) - Scarlet. 2001.
- Marti Caine (s) - Crimson. Beane, 1996.
- Mary Cynthia (s) - Cream flushed on salmon. 2010.
- Mary Lou Heard (s) - Bicolour. 2004.
- Mary Malcolm (s) - Delicate apricot salmon. 1955?
- Mary Pannell - synonym of Daily Mail
- Mary Rose (s) - Rose pink. 1997.
- Masterpiece (s) - Rosy lavender. Malcolm, 1910.
- Matchmaker (s) - A series of six bicolours. Hem Zaden, 2012.
- Matucana (g) - Maroon/purple bicolour from Peru. Harland, c.1955.
- Maudie Best (s) - Maroon. Malin, 1973.
- Maudie Winfield (s) - Maroon.
- Mauve King (s) - Mauve. 1991.
- Mauve Queen (g) - Mauve standard, bluish mauve wings. Eckford, 1887.
- May Campbell (s) - Carmine rose flake, cream ground. 1912.
- Maytime (s) - Rose pink, white ground. 1979.
- Memorial Flight (s) - White. King, 1998.
- Memories (s) - Rose pink. Davis, 1990.
- Memories(3) (g) - Purple mauve. 2005.
- Memory (e) - A lavender Spencer Praecox variety.
- Midnight (s) - Dark maroon. B.R.Jones, 1986.
- Midnight Star (s) - Flake. 1998.
- Milestone (s) - Maroon. 1971.
- Millennium (s) - Crimson. D.M.Jones, 2000.
- Milly (s) - Magenta. 2007.
- Minnie (e) - A navy blue EMG sweet pea.
- Min's Ambition (s) - Magenta. Woodcock, 1993.
- Miranda (e) - A crimson EMG.
- Miranda Crafer (s) - Magenta. Walker, 1996.
- Miss Burnie (s) - Blush pink, white ground. 1916.
- Miss Truslove (s) - A pale mauve sweet pea. Truslove, 1991.
- Miss Willmott (g) - Salmon-pink bicolour. Eckford, 1901.
- Misty (s) - Mauve flush. Leese, 2008.
- Misty Mountain (s) - Pale mauve. Evans, 2004.
- MM (s) - Cerise. Grayson, 1999.
- Mollie Rilstone (s) - Pink picotee, cream ground. Tremewan, 1993.
- Molly Cuer (s) - Pale blue. Tullett, 1999.
- Monarch (e) - A Spencer Praecox.
- Monarch's Diamond (s) - Pink picotee, cream ground. Woodcock, 1987.
- Monty Don (g) - Dark maroon. Parsons, 2008.
- Moonlight(1) (e) - A deep blue Spencer Praecox variety.
- Moonlight(2) (s) - Lavender flush, white ground. 2011.
- Moorland Beauty (s) - Rich mauve with large flowers. Albutt, 1995.
- Moorland Mist (s) - Pale lavender. Albutt, 1998.
- More Scent - Purple fush, white ground. Hammett, 2012.
- Morning Rose (s) - Pale pink. Kershaw, 1980.
- Morven (s) - Orange-red. Chisholm, 1998.
- Mother of Pearl - Synonym of Blue Shift.
- Mount Stewart (s) - Mauve. Harrod, 2005.
- Mrs Bernard Jones (s) - Rose pink, white ground. B.R.Jones, 1981.
- Mrs C Kay (s) - Lavender. 1939.
- Mrs Chris James (s) - Rose pink.
- Mrs Collier (g) - Cream. Dobbie, 1906.
- Mrs Cuthbertson (s) - Rose pink bicolour. Dobbie, 1911.
- Mrs Douglas MacArthur (e) - A salmon Spencer Praecox.
- Mrs Jaqui Jones (s) - Navy blue. 2003.
- Mrs Jemma Stead (g) - Pale blue flush, white ground. Grayson, 2011.
- Mrs Joan Ward (s) - Rose pink. Woodcock, 1996.
- Mrs June Grayson - Magenta. Grayson, 1997.
- Mrs R Bolton (s) - Rose pink, white ground. 1945-6.
- Mrs R Chisholm (s) - White. Chisholm, 2009.
- Mrs Walter Wright (g) - Deep mauve. Eckford, 1903.
- Mumsie (s) - Crimson. 1993.
- My Navy (s) - Navy blue. Hammett, 2010.
- Myfanwy Townsend (s) - Scarlet. 2002.
- Myrtle Mann (s) - Orange-red. 1993.