 | Oak Hill Gardens ENGLISH Diverse selection of orchid species and hybrids offered. Established in 1973. Liese Pigors-Butler, Greg Butler, Hermann Pigors. Dundee, Illinois, USA.  | | |
| Oak Knob Orchids ENGLISH Specializing in Cattleya and Vanda allied plants. Hybrids and species. Bardstown, Kentucky, USA. | | |
| Oasis the Journal ENGLISH Quarterly publication covering aspects of many species and genera, from a wide range of geographical areas. Eco tours and online book store. Rod Rice. Dora Creek, New South Wales, Australia. | | |
| Ocean Orchids SLOVENIAN / ENGLISH Wholesale potted orchid grower concentrating on markets in Slovenia, Hungary, Italy, and Croatia. Established in 2003. Dobrovnik, Slovenia. | | |
| Odom's Orchids ENGLISH Specializing in Cattleya and Phalaenopsis mericlones and seedlings. John and Louise Odom. Fort Pierce, Florida, USA. | | |
 | Odontoglossum Alliance ENGLISH International organization devoted to the exchange of information about orchids in the Odontoglossum alliance. Quarterly journal published. | | |
| OFE International ENGLISH Large selection of supplies for growing orchids. Carlos A. Cahiz. Miami, Florida, USA. | | |
 | Okinawan Orchis JAPANESE / ENGLISH Information (including photos) about Amitostigma lepidum (Okinawan orchis). Okinawa, Japan. | | |
| Olomana Orchids ENGLISH Selection of orchid genera offered including Dendrobium, Oncidium, and Cattleya. Peter Neifert. Kaneohe, Hawaii, USA. | | |
| Olympia Orchids ENGLISH Phalaenopsis hybrids and species offered. Lab services offered to hobby hybridizers. Bill Tippit. Friendswood, Texas, USA. | | |
| Only Orchids ENGLISH Orchid arrangements for businesses, the home, special events, or as gifts. Free delivery between Los Altos and Burlingame. Maintenance programs available. Portola Valley, California, USA. | | |
| Orange County CA Branch - CSA ENGLISH Branch of the Cymbidium Society of America. Contact, meeting and awards information. Garden Grove, California, USA. | | |
| Orchid ENGLISH Blog covering a variety of orchid topics including growing in the tropics, photos, culture, nursery, and Internet resources. Soerjo Winarto. Cileungsi, West Java, Indonesia. | | |
| Orchid RUSSIAN Digital periodical covering a diverse range of orchid topics. Photo gallery and discussion forum. Russia. | | |
| Orchid Academy ENGLISH Providing illustrated correspondence courses about orchid growing for newcomers to the world of orchids and for more advanced growers and those seeking employment in the orchid industry. Author of 'Growing Orchids in Your Garden' (Timber Press, 2004). Lili and Robert Friend. Main Beach, Queensland, Australia. | | |
| Orchid Care Services ENGLISH Potting mixes and growing media from Australian materials. Werner Deisel. Oakville, New South Wales, Australia. | | |
| Orchid Club Labellum ENGLISH / CZECH Orchid species, hybrids, and greenhouse photographs. Roman Maruska. Chrastava, Czech Republic. | | |
| Orchid Conservation Alliance ENGLISH The primary objective of The Orchid Conservation Alliance is to promote the conservation of wild orchid species in their native habitats. The current goal is to purchase 100 hectares of undisturbed orchid habitat in the high Andes of Ecuador. | | |
| Orchid Conservation Coalition ENGLISH Grassroots organization made up of people, orchid societies, and orchid businesses dedicated to raising awareness and money for orchid conservation. | | |
| Orchid Conservation International ENGLISH Conceived in 2003 by a small group of UK-based orchid experts. Orchid Conservation International is an independent, non-profit organization established to provide a firm funding base for the work of the Orchid Specialist Group (OSG). | | |
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