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- Allium obliquum: Twistedleaf Garlic
- Allium obtectum
- Allium obtusum: Red Sierran Onion
- Allium ochotense
- Allium ochraceum
- Allium ochroleucum
- Allium odoratissimum
- Allium odorum
- Allium oleraceum: Field Garlic
- Allium oleraceum ssp. girerdii
- Allium olivieri
- Allium oltense
- Allium olympicum
- Allium omeiense
- Allium omiostema
- Allium opacum
- Allium ophiophyllum
- Allium ophiopogon
- Allium oporinanthum
- Allium oreodictyum
- Allium oreophiloides
- Allium oreophiloides ssp. salangense
- Allium oreophilum
- Allium oreoprasoides
- Allium oreoprasum
- Allium oreoscordum
- Allium orientale
- Allium orunbaii
- Allium ostrowskianum ( A oreophilum 'Ostrowskianum')
- Allium otschiauriae
- Allium ousensanense
- Allium ovalifolium
- Allium ovalifolium var. leuconeurum
- Allium ovatum
- Allium oviflorum
- Allium ownbeyi
- Allium oxyphilum: Lillydale Onion
Read more about this topic: List Of Allium Species