| Cultivar Name | Plant Size | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Odina' | Large | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Oglala' | Giant | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Ohio Blue' | - | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Ojibway' | Medium | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Old Hump Back' | Large | Dark-Green | - | - | Hybrid | Pale-Lavender | June into July | Wade, Van | .1999 |
| 'Old Rough House' | Giant | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Olga Gibosa' | Large | Med-Green | - | - | Unknown | Light-Purple | July into August | Wade, Van | --NR-- |
| 'Omaha' | Large | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Oneida' | Medium | Med-Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Ontario Blue' | Large | Blue/Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
| 'Open Hearted' | Giant | Blue/Green | - | - | Unknown | - | July | Wade, Van | .1999 |
| 'Ottawa' | Large | Med-Green | - | - | Unknown | - | - | Wade, Van | --NR-- |
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