Plant WitchPlants: O
- Oak Fern Gymnocarpium dryopteris Fern
- Oakleaf Hydrangea Hydrangea quercifolia Flowering shrub
- Oat Avena sativa Grain
- Obedient Plant Physostegia virginiana Garden perennial
- Oca Oxalis tuberosa Root
- Oceanspray Holodiscus discolor Flowering shrub
- Oconee Azalea Rhododendron flammeum Flowering shrub
- Ocotillo Fouquieria splendens Succulent
- October Daphne Hylotelephium sieboldii Creeping perennial
- Ogeechee Tupelo Nyssa ogeche Flowering tree
- Ohio Buckeye Aesculus glabra Flowering tree
- Ohio Goldenrod Oligoneuron ohioense
- Ohio Spiderwort Tradescantia ohiensis Wildflower
- Okra Abelmoschus esculentus Fruiting
- Oleander Nerium oleander Flowering shrub
- Olive Olea europaea Tree fruit
- Oneflower Helianthella Helianthella uniflora Wildflower
- Oneleaf Onion Allium unifolium Allium
- Onion Allium cepa Allium
- Orach Atriplex hortensis Leafy
- Orange Citrus sinensis Tree fruit
- Orange Coneflower Rudbeckia fulgida Wildflower
- Orange Honeysuckle Lonicera ciliosa Flowering shrub
- Orange Ice Plant Lampranthus aurantiacus Creeping perennial
- Orange Lily Lilium bulbiferum Garden perennial
- Orange River Lily Crinum bulbispermum Bulb
- Oregano Origanum vulgare Herb
- Oregon Checkerbloom Sidalcea oregana Wildflower
- Oregon Grape Mahonia aquifolium Berry
- Oregon Iris Iris tenax Wildflower
- Oregon Stonecrop Sedum oreganum Creeping perennial
- Oregon White Oak Quercus garryana Nut
- Oriental Poppy Papaver orientale Garden perennial
- Orpine Hylotelephium telephium Succulent
- Oshima Sedge Carex oshimensis Grass sedge
- Osteospermum Osteospermum ecklonis Garden perennial
- Ostrich Fern Matteuccia struthiopteris Leafy
- Oxblood Lily Rhodophiala bifida Bulb
- Oxeye Sunflower Heliopsis helianthoides Wildflower