- Oban Bay (s) - A lovely pale ice blue sweet pea. Chisholm, 1997.
- Oklahoma (s) - Crimson flake. 2002.
- Ola (s) - Pale mauve. 1999.
- Old Times (s) - Blue flush.
- Olive D (s) - Maroon stripe. Rowland, 2008.
- Oliver Cromwell (s) - Maroon. 2000.
- Olivia Faraday (g) - A mauve old fashioned sweet pea. Grayson, 2004.
- Olympic Flame (s) - Salmon-cerise flush. Harrod.
- Orange Dragon (s) - Bright orange sweet pea with smallish flowers.
- Orange Surprise (s) - Orange bicolour.
- Orchid (s) - Veined light lavender. 2008.
- Our Colin (s) - Mid blue. Chisholm, 2009.
- Our Harry (s) - Similar to 'Noel Sutton', this mid blue sweet pea is less prone to marking in damp weather. Davis.
- Our Jenny (s) - Mid blue. 1993.
- Our Joyce (s) - Orange-pink. 1984.
- Ouse Valley (s) - A very vigorous lavender sweet pea which tends to have rather coarse, gappy stems. Tasker.
- Oxford Blue (s) - Opens mid blue and then darkens. 2001.