- Karen Harrod (s) - Mid blue. Harrod.
- Karen Louise (s) - Lavender. 1998.
- Karen Reeve (s) - An older maroon sweet pea with large flowers, but stems go short early in the season.
- Karen Tremewan (s) - Orange-pink. Tremewan.
- Kathleen (e) - A rich clear orange Cuthbertson Florabunda variety. Cuthbertson.
- Katie (e) - A Cuthbertson Florabunda with rose pink flowers on a cream ground. Cuthbertson.
- Katie Alice (s) - Mauve. 2006.
- Kelvedon Beauty (s) - Mauve. 2005.
- Ken Colledge (s) - Mauve.
- Kenneth (e) - A crimson Cuthbertson Florabunda sweet pea. Cuthbertson.
- Kernow (s) - Scarlet. Tremewan, 1986.
- Kiera Madeline - Cream picotee sweet pea. Heathcote, 2009.
- King Edward VII (g) - Crimson. Eckford, 1903.
- King of the Mauves (s) - A very old mauve sweet pea from the now defunct firm of Woodcock.
- King Size Navy Blue - Dark blue.
- King's Bounty - Magenta.
- King's Bride - Rose pink on cream ground.
- King's Cloak - Dark blue.
- King's Frill (s) - Picotee.
- King's Reach - Mid blue. 1993.
- Kippen Cream (s) - Cream. Chisholm, 1998.
- Kiri Te Kanawa (s) - Rose pink. 1995.
- Kitty Hawk (s) - Cerise. 2003.
- Kyle the Clown (s) - Cerise stripe. Chisholm, 2001.