1. A
2. B
3. C
4. D
5. E
6. F
7. G
8. H
9. I
10. J
11. K
12. L
13. M
14. N
15. O
16. P
17. Q
18. R
19. S
20. T
21. U
22. V
23. W
24. X
25. Y
26. Z

1. Oak Leaf Ivy Also known as: Cissus rhombifolia 'Manda Supreme'
2. Oakleaf fern Also known as: Drynaria rigidula
3. Oakleaf ferns Also known as: DRYNARIA
4. Obregonia denegrii Also known as: Artichoke Cactus
5. OCHNA Also known as: Bird's Eye Bush
6. Ochna serrulata Also known as: Mickey Mouse Plant
7. OCIMUM Also known as: Basil
8. Ocimum basilicum 'Green Globe' Also known as: Sweet Basil
9. Ocimum basilicum 'Opal' Also known as: Basil
10. Ocotillo Also known as: Spider Cactus, Fouquieria Splendens
11. Octopus Plant Also known as: Candelabra Aloe, Torch Plant, Aloe arborescens
12. Odontoglossum grande Also known as: Tiger Orchid
13. Odontoglossum pulchellum Also known as: Lily of the Valley Orchid
14. Oilcloth Flower Also known as: Painters Palette, Anthurium andraeanum
15. Okra Also known as: Abelmoschus Esculentus
16. Old Maid Also known as: Periwinkle, CATHARANTHUS
17. Old Man Cactus Also known as: Cephalocereus senilis
18. Old Man Of the Andes Also known as: BORZICACTUS
19. Old Mans Beard Also known as: Fringe Tree, Chionanthus Virginicus
20. Oleander Also known as: Rosebay, Nerium Oleander
21. Oleander Also known as: Nerium oleander hybrids
22. Olive Also known as: Olea europaea
23. Olive Tree Also known as: Olea Europaea
24. ONCIDIUM Also known as: Dancing Lady Orchid
25. Oncidium ampliatum majus Also known as: Turtle Orchid, Yellow Tree
26. Oncidium lanceanum Also known as: Cedros Bee, Leopard Orchid
27. Oncidium papilio Also known as: Butterfly Orchid
28. Oncidium sphacelatum Also known as: Golden Shower
29. Oncidium splendidum Also known as: Dancing Girls Orchid
30. Onion Also known as: ALLIUM
31. Onions Also known as: Yellow Onion, Alium Cepa
32. Opera Gardenia Also known as: China Flower, Gardenia jasminoides
33. OPHIOPOGON Also known as: Lily-turf, Snake's beard
34. Ophiopogon planiscapus nigrescens Also known as: Black Dragon
35. OPLISMENUS Also known as: Basketgrass
36. Oplismenus hirtellus 'Variegatus' Also known as: Variegated Basketgrass
37. OPUNTIA Also known as: Prickly Pear
38. Opuntia basilaris Also known as: Beavertail Cactus
39. Opuntia littoralis Also known as: Prickly Pear Cactus
40. Orange Corn Cob cactus Also known as: Lobivia winteriana
41. Orange Jessamine Also known as: Bark Tree, Murraya paniculata
42. Orange Star Also known as: Guzmania lingulata
43. ORBEA Also known as: Carrion Flowers
44. Orchid Cactus Also known as: Epiphyllum hybrids
45. Oregano Also known as: Origanum vulgare
46. Oregano Also known as: Wild Majoram, Origanum Vulgare
47. Oregon Grape Also known as: Grape Holly, Mahonia Aquifolium
48. Oriental Water Fern Also known as: Frog Vegetable, Water Fern, Ceratopteris thalictroides
49. Origanum majorana Also known as: Sweet Marjoram
50. Origanum Marjorana Also known as: Sweet Marjoram
51. Ornamental Grass Also known as: Fescue, Festuca
52. Ornamental Pepper Also known as: Cayenne, CAPSICUM
53. Ornithogalum arabicum 'Dubium' Also known as: Star of Bethlehem
54. Ornithogalum caudatum Also known as: False Sea Onion, Pregnant Onion
55. Ornithogalum nutans Also known as: Drooping Star of Bethlehem
56. Ornithogalum umbellatum Also known as: Betty Go to Bed at Noon
57. OSMANTHUS Also known as: Tea Olive
58. Osmanthus fragrans Also known as: Sweet Olive
59. Osmanthus heterophyllus 'Variegatus' Also known as: Variegated False Holly
60. Osmorhiza Also known as: Sweet Cicely, Sweetroot
61. Ostrich Fern Also known as: Garden Fern, Matteuccia Struthiopteris
62. OTATEA Also known as: Weeping Bamboo
63. Otatea acuminata Also known as: Mexican Weeping Bamboo
64. Our Lady's Tears Also known as: Jacobs Ladder, Ladder to Heaven, Lily of the Valley, Convallaria majalis
65. Owl's Eyes Also known as: Mammillaria parkinsonii
66. OXALIS Also known as: Shamrock, Wood Sorrel
67. Oxalis corymbosa Also known as: Pink Sorrel
68. Oxalis regnelii Also known as: Lucky Clover