| 2842 | O MY GOODNESS | Zurbrigg, L. 1970/73 | TB | 36 | E | Self | RARE S:buff yellow with imbricata flush of violet, F:buff yellow with violet stripes, gold haft, B: yellow | 6.00 |
| 4266 | OCELOT | Ghio, J. 1997/98 | TB | 36 | EM | Bicolor | S:peach, F:maroon with blackish sheen, B:tangerine | NFS |
| 2321 | OCHRACEA CAERULEA | Denis, F. 1919/19 | TB | ML | Blend | S:golden yellow infused lavender, F:lavender violet with thin yellow rim, blue streak, white lines at haft, B:yellow; fragrant | NFS | |
| 283 | OCTOBER BLAZE | McDade, C. 1934/35 | TB | E,Re | Self | RARE Deep red violet self | 5.00 | |
| 1656 | ODORATISSIMA | Jacquin, N. 1797/97 | TB | M | Self | S:lavender violet, F:slightly darker, lighter at haft, B:white, orange tipped at base; sweet fragrance, vigorous | SO | |
| 2939 | OKLAHOMA | Mitchell, S. 1945/45 | TB | L | RARE Soft shade of old gold, deeper at hafts with maroon lines, cream around B, light violet blaze, B:yellow; good fragrance | NFS | ||
| 553 | OKLAHOMA BANDIT | Nichols, H. 1979/80 | IB | 22 | M-L | Self | S:bright tawny gold, claret base, F:same, washed claret, B:orange-bronze; ruffled | 5.00 |
| 2326 | OKTOBERFEST | Maryott, W. 1985/87 | TB | 37 | M | Self | Heavily ruffled red-orange; B:orange | 8.00 |
| 573 | OLA KALA | Sass, J. 1942/43 | TB | 38 | M | Self | Heavily ruffled dark yellow; very vigorous and prolific, Dykes Medal 1948 | 5.00 |
| 3813 | OLD BLACK MAGIC | Schreiner 1996/96 | TB | 36 | EM | Self | Lightly ruffled coal black self, B:yellow gold; pronounced sweet fragrance | NFS |
| 608 | OLD FLAME | Ghio, J. 1973/75 | TB | 36 | ML | Self | Chalk white with thin yellow edge on all petals, B:red | 6.00 |
| 2464 | OLIVE ORCHID | Austin, L. 1956/57 | TB | 40 | L | Self | RARE Pale lilac blue, deep lilac flush at end of B. olive veins on white ground at sides of bright yellow beard | 5.00 |
| 1120 | OLYMPIAD | Ghio, J. 1983/84 | TB | 38 | E-L | Bitone | S:pale blue, darker blue in center, F:light blue with mid-blue wash through center, B:light blue | 7.00 |
| 1468 | OLYMPIC CHALLENGE | Schreiner 1985/85 | TB | 38 | EM | Self | Lightly ruffled uniform rich orange, half dollar size white area surrounding rich tangerine red B; beautiful and very popular | 8.00 |
| 2413 | OLYMPIC PINK | Gibson, J. 1984/85 | TB | 36 | ML | Self | Ruffled, fluted, and laced pink with blue cast, B:red | NFS |
| 378 | OLYMPIC TORCH | Schreiner 1956/58 | TB | 38 | L | Self | RARE Ruffled light golden bronze | NFS |
| 2680 | OMINOUS STRANGER | Innerst, S. 1992/93 | TB | 34 | M | Plicata | S:muted yellow trimmed muted purple, brown dots, F:muted yellow trimmed muted purple, tiny brown dots over all, B:bronze; slight frag | 8.00 |
| 260 | ON EDGE | Schreiner 1986/86 | TB | 37 | EM | Plicata | S:light lavender, stitched pale lavender-blue on inside, F:white, edged deep violet-purple; B:old gold | 7.00 |
| 2080 | ON FIRE | McClintock, V. 1979/80 | SDB | 12 | M | Self | Full orange-red, B:deep blue-violet | NFS |
| 1985 | ON LINE | Schreiner 1980/80 | TB | 36 | EM | Self | RARE S:light blue with pronounced blue purple brushing along midrib to deep blue central streak on F, B:blue tinged gold | NFS |
| 4291 | ON TARGET | Knopf, B. 1969/70 | TB | 36 | M-L | Self | RARE Mimosa yellow self, B:yellow; fluted | NFS |
| 870 | ON THE GO | Plough, G. 1973/74 | TB | 29 | E-L | Plicata | RARE S:white, blending to hyacinth blue plicata pattern, F:white, heavily marked haft of brown heliotrope, edged part-way down F, B:orange | 5.00 |
| 2149 | ONE ACCORD | Ensminger, A. 1981/82 | SDB | 14 | E | Bitone | RARE S:cobalt blue, F:campanula violet, B:hyacinth blue | 4.00 |
| 238 | ONE DESIRE | Shoop, G. 1960/60 | TB | 34 | EM | Self | RARE Deep rich pink, B:pink | NFS |
| 4038 | ONE STEP BEYOND | Tasco, R. 2014/14 | TB | 34 | M | Bicolor | S:oxblood red, bronze lower midrib, F:velvety jet black, yellow veins at haft, B:golden orange, purple black hairs at end; ruffled, spicy fragrance, pbf | NFS |
| 1038 | OOS AND AHS | Ensminger, A. 1973/77 | TB | 36 | M-L | Self | RARE Pale blue, splashed dark violet, B:yellow; no two blossoms have the same color arrangement | 6.00 |
| 2679 | OPALINE | Williamson, E. B. 1928/28 | TB | ML | Self | RARE Orchid lavender with pink highlights, S:white at haft with lavender veins in center, light maroon veins at edges, B:white base, yellow tips | 5.00 | |
| 3052 | OPEN YOUR EYES | Black, P. 2010/10 | SDB | 15 | ML | Halo | S:white, pale blue irregular patches, F:white, large irregular inky dark blue spot, white darts in throat, B:white; strong sweet fragrance | 4.00 |
| 1412 | OPENING NIGHT | Gibson, J. 1969/70 | TB | 42 | EM | Bitone | RARE S:velvet black-purple, F:darker, B:lively purple; ruffled | NFS |
| 3155 | ORANGE CHARIOT | Fay, O. 1962/64 | TB | 36 | M | Self | RARE Light orange self, pink blush, B:Chinese coral | NFS |
| 1073 | ORANGE CRUSH | Suiter, M. 1957/59 | TB | 38 | ML | Self | RARE Burnt orange self, large bloomed with serrrated edges, B:bushy red-orange; GBF | 5.00 |
| 460 | ORANGE EMPIRE | Hamner, B. 1973/74 | TB | 37 | M-L | Self | Ruffled brilliant orange, B:saturn red | 6.00 |
| 1933 | ORANGE GEM | McKee,W. 1948/48 | TB | 38 | M | Self | RARE Rich dark yellow-orange | 5.00 |
| 309 | ORANGE GLORY | Jones, B. 1973/74 | TB | 35 | M | Self | RARE Ruffled and laced orange with buff influence, B:red-orange | 6.00 |
| 1701 | ORANGE HONEY | Zurbrigg, L. 1976/76 | TB | 36 | M,Re | Self | RARE Apricot with some blending of yellow at haft, B:red; Oct. rebloom | NFS |
| 2682 | ORANGE JEWELIUS | Miller, D. 1990/91 | TB | 36 | ML | Bitone | S:creamy orange, F:orange blended yellow, slight pink tones, B:red | 8.00 |
| 2791 | ORANGE PARADE | Hamblen, M. 1958/61 | TB | 38 | M-L | Bitone | S:marigold orange, F:Spanish orange, B:orange red | 5.00 |
| 2744 | ORANGE PLUME | Gibson, J. 1978/79 | TB | 38 | M | Plicata | Ruffled orange plicata with small white signal patch, B:orange | NFS |
| 2792 | ORANGE POPSICLE | Sutton, G. 1987/87 | TB | 33 | E-M | Self | Ruffled and laced creamy orange, B:tangerine,; pronounced sweet fragrance | NFS |
| 2428 | ORANGE TWOTONE | Austin, L. 1954/54 | IB | 24 | E | Self | RARE Yellow orange with dark wash of brown on F | 5.00 |
| 2096 | ORBITER | Aitken, T. 1985/85 | TB | 38 | EM | Self | Blue-purple, B:frosted blue-purple, pronounced sweet fragrance | 7.00 |
| 3857 | ORCHID AND FLAME | Craig, T. 1954/54 | TB | 45 | EE,Re | Self | RARE Hyacinth orchid self, B:flaming tangerine | NFS |
| 944 | ORCHID BLUSH | Brown, J. 1980/81 | TB | 35 | M | Self | Laced and lightly ruffled light orchid with slightly darker veining on F, B:orange, tipped orchid | 7.00 |
| 2835 | ORCHID DANDY | Tucker, J. 1971/72 | TB | 35 | E-L | bitone | RARE S:orchid, suffused yellow at base, F:light lavender, white center, gold shoulders, B:bright yellow; laced | 6.00 |
| 1934 | ORCHID LADY | Salbach, C. 1942/43 | TB | 36 | ML | Self | RARE Stately ruffled orchid-pink and copper; flaring falls | SO |
| 4343 | ORCHID RUFFLES | Schreiner, R. 1954/54 | TB | 34 | M | Self | RARE Light orchid self | NFS |
| 396 | OREGON SUNSHINE | National Iris 1939/39 | TB | 31 | EM | Bitone | RARE S:light lemon yellow, F:lemon yellow, tan lines at haft, faint lav. wash on F, B:bushy yellow orange | 5.00 |
| 1935 | ORELIO | DeForest, F. 1947/47 | TB | 36 | M | Self | Big flowers of bright brownish red; distinct hue and silken finish with broad petals | 5.00 |
| 1127 | ORIENTAL IMAGERY | Black, P. 1984/85 | TB | 33 | EM | Bicolor | RARE S:flesh pink, orchid overtones deepening to top, F:pale lavender orchid, white area around B, 1/2" lav.edge, B:tangerine; ruffled, fragrant | 7.00 |
| 542 | ORINOCO FLOW | Bartlett, C. 1989/93 | BB | 25 | EM-L | Plicata | RARE S:white, heavily stitched deep purple blue on edge, F:white, heavy plicata markings at haft & top edge, B:navy blue; heavily ruffled, fragrant | 8.00 |
| 2446 | ORLOFF | Sass, H. 1931/37 | TB | 32 | LM | Plicata | RARE S:heavily veined appears rich brown, F:cream stitched and dotted bronze. Brilliant cinnamon purple plicata | 5.00 |
| 628 | OSAGE BUFF | Gibson, J. 1972/73 | TB | 36 | M | Plicata | RARE S:apricot with garnet red flush, F:apricot with garnet red stitching and specks, B:poppy red; ruffled | NFS |
| 2760 | OSAKA | Ghio, J. 1991/93 | TB | 42 | EM | Bicolor | S:white, cream center, F:maroon red, slight violet blaze, B:yellow | 10.00 |
| 2684 | O'SO PRETTY | Kegerise, E. 1992/93 | TB | 31 | EM | Bitone | S:lilac tinted white, fading white, F:tinted lilac, fading to white in center, edged deep lilac, B:white, tipped lilac; ruffled, sweet frag | 8.00 |
| 2815 | OTHELLO | Lemon, J. 1848/48 | BB | M | Bitone | S:purple spectrum violet, F:velvety fluorite, veined reddish brown on lav haft, B:orange | NFS | |
| 3377 | OTHER VOICES | Markham, L. 2004/05 | TB | 34 | M | Bitone | S:greenish ivory, light gold edges, faint purple flush at base, F:warm cream, green shading to edge, bright gold hafts, B:deep gold; ruffled, spicy fragrance | NFS |
| 1371 | OUT YONDER | Wickersham, G. 1969/69 | TB | 36 | M | Bitone | RARE S:pale blue, F:solid indigo blue with slight violet cast, B:white, tipped pale yellow | 5.00 |
| 474 | OVATION | Tompkins, C. 1969/69 | TB | 35 | ML | Self | Dark bright pink; very beautiful but can't get it to grow for me | NFS |
| 4023 | OVERFLOWING HEART | Jedlicka, L&K 2012/13 | TB | 34 | EM | Bicolor | S:pink, style arms pink with white stripes, F:large pink starburst around beard, white flash, wide medium purple boarder, B:orange, white end; ruffled, sweet fragrance | NFS |
| 2970 | OVERTURE | Hall, D. 1944/44 | TB | M | Self | RARE Light pink from two pink blend seedlings. | NFS |
