| Cultivar Name | Plant Size | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Occupy Wall Street' | Small | Blue/Green | Marginal | White | Unknown | - | July into August | Freeman, Franc | .2012 |
| 'Odyssey' | Medium | Dark-Green | Streaked | Speckles | Hybrid | - | July | Arnold, Beth | .1999 |
| 'Ogon Muraski' | Small | Yellow | - | - | Unknown | Light-Purple | July | Unknown | --NR-- |
| 'Ogon Otome' | Small | Yellow | - | - | Unknown | Deep-Purple | July | Unknown | --NR-- |
| 'Ohh! Lovilia' | Large | Yellow | - | - | Unknown | Near-White | June into July | Schulz, Ed | .2015 |
| 'Okobaji' | Small | Blue/Green | - | - | Unknown | - | - | Tompkins, Chet & Ruh, Peter & Jean | .2008 |
| 'Old Ironsides' | Giant | Light-Green | - | - | Nat-Sport | Med-Lavender | July | Summers, Alex | --NR-- |
| 'Olympic Fab Five' | Medium | Yellow | - | - | Unknown | - | July into August | Freeman, Franc | .2012 |
| 'One and Only' | Large | Yellow | - | - | Hybrid | Pale-Lavender | June into July | Ward, Dr Dick & Jane | .2015 |
| 'One Fine Day' | Medium | Med-Green | Marginal | Yellow | Hybrid | Near-White | June into July | Ward, Dr Dick & Jane | .2012 |
| 'Osiris Prestige' | Medium | Dark-Green | Medial | White | Unknown | Pale-Lavender | - | Fafard, Serge | --NR-- |
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