• Ocimum basilicum
• Ocimum basilicum ‘Magic Mountain’
• Oenothera ‘African Sun’
• Oenothera biennis
• Oenothera fruticosa ‘Fyrverkeri’
• Oenothera lamarckiana
• Oenothera macrocarpa
• Oenothera odorata ‘Apricot Delight’
• Oenothera pilosella ‘Yella Fella’
• Oenothera speciosa ‘Siskiyou’
• Omphalodes cappadocica ‘Cherry Ingram’
• Omphalodes verna
• Omphalodes verna ‘Alba’
• Onobrychis viciifolia
• Ononis spinosa
• Ophiopogon benoistii
• Ophiopogon bodinieri
• Ophiopogon chingii
• Ophiopogon intermedius
• Ophiopogon japonicum ‘Digital Mining’
• Ophiopogon japonicum ‘Silver Comet’
• Ophiopogon japonicus ‘Minor’
• Ophiopogon japonicus ‘Sparkler’
• Ophiopogon planiscapus ‘Black Dragon’
• Ophiopogon planiscapus ‘Niger’
• Ophiopogon planiscapus ‘Olivaceus’
• Origanum ‘Bellissimo’
• Origanum ‘Dingle Fairy’
• Origanum ‘Rosenkuppel’
• Origanum laevigatum ‘Herrenhausen’
• Origanum laevigatum ‘Purple Charm’
• Origanum majorana
• Origanum vulgare
• Origanum vulgare ‘Album’
• Origanum vulgare ‘Compactum’
• Origanum vulgare ‘Hot Spicy’
• Origanum vulgare ‘Thumble’s Variety’
• Ornithogalum nutans
• Ornithogalum ponticum ‘Sochi’
• Orostachys iwarenge ‘Chinese Hat’
• Oxalis acetosella
• Oxalis magellanica ‘Nelson’