- Ordóñez-García, Magali
- Ordóñez-Garza, Nicté
- Ordóñez-López, Uriel
- Ordóñez-Reséndiz María Magdalena
- Ordorica Hermosillo, Antonio
- Ordoyno, Thomas.
- Ordubegian, Liza
- Orduz, Sergio
- Ordway Seed and Farm Company.
- Ordway, Ellen, 1927-2018
- Ordway, John Morse, 1823-1909
- Ordynets, Alexander
- O'Rear, David M., 1929-
- Orecchia, Paola
- Oregan, D
- Oregon Botanical Expedition.
- Oregon Bulb Farms.
- Oregon Camellia Society.
- Oregon Climate Change Institute
- Oregon Conservation Commission.
- Oregon Florists' Seed Company.
- Oregon Gardens (Portland, OR)
- Oregon Gardens (Portland, Or.)
- Oregon Glad Gardens.
- Oregon Natural Heritage Program.
- Oregon Nursery Co.
- Oregon Nursery Company.
- Oregon Ranch, Inc.,
- Oregon Seed Store.
- Oregon State Board of Forestry.
- Oregon State College. Agricultural Experiment Station.
- Oregon State Highway Commission.
- Oregon State Horticultural Society.
- Oregon State University.
- Oregon State University. Agricultural Experiment Station.
- Oregon State University. College of Forestry.
- Oregon State University. Department of Botany and Plant Pathology.
- Oregon State University. Department of Rangeland Resources.
- Oregon State University. Extension Service.
- Oregon State University. Forest Research Laboratory.
- Oregon State University. Herbarium.
- Oregon Wholesale Nurseries.
- Oregon.
- Oregon. Board of horticulture.
- Oregon. Board of Horticulture.
- Oregon. Bureau of statistics.
- Oregon. Department of Environmental Quality.
- Oregon. Department of Fish and Wildlife.
- Oregon. Department of Forestry.
- Oregon. Dept. of commercial and industrial service.
- Oregon. Dept. of Fish and Wildlife.
- Oregon. Dept. of Forestry.
- Oregon. Dept. of State Police.
- Oregon. Office of Superintendent of Public Instruction.
- Oregon. Office of the Secretary of State.
- Oregon. Stallion registration board.
- Oregon. State Biologist.
- Oregon. State biologist.
- Oregon. State Board of Fish and Game Commissioners.
- Oregon. State board of forestry.
- Oregon. State Dairy and Food Commissioner.
- Oregon. State Department of Agriculture.
- Oregon. State Game Commission.
- Oregon. State immigration commission.
- Oregon. State live stock sanitary board.
- O'Reilly, Bernard.
- O'reilly, Catherine M
- O'Reilly, Myles
- O'reilly, Peter S
- O'reilly, Ralph
- O'reilly, S Y
- O'Reilly, Suzanne Y
- Orejarena, Jaime
- Orejas-Miranda, B R
- Orejas-Miranda, Braulio
- Orejuela, Andrés
- Orejuela, Catalina
- Orejuela, Jorge E
- Orekhovich, V. N. (Vasiliĭ Nikolaevich) 1904-
- Orel, George
- Orel, Harvey K
- Orell, P
- Orell, Peter
- Orellana Liebbe, María Cristina
- Orellana, Fernanda I
- Orellana, Francisco
- Orellana, Francisco A
- Orellana, José Alfredo Vicente
- Orellana, José I
- Orellana, José I.
- Orellana, Mónica V.
- Orellana-B., Andrés M.
- Orellana-Halkyer Nancy
- Orellana-Torres, Andrés
- Orelli, Marcus von
- Oremans, Philippe
- Oren, Aharon
- Oren, D
- Oren, David C
- Oren, David C.
- Oren, Muhammet
- Orenco Nursery Company.
- Orendt, C
- Orensanz, José M
- Orensanz, Juancho
- Orenstein, A. J.,
- Orenstein, Alexander Jeremiah, 1879-
- Orenstein, Ronald I
- Orenstein, Ronald I. (Ronald Isaac), 1946-
- Oreshkina, Tatiana V
- Orey, Dave.
- Orfão, Laura Helena
- Orfila, Ricardo N
- Organ, John F.
- Organ, Kenneth K
- Organ, Michael K
- Organic Flower Farm,
- Orge, Maria Dolores Ribeiro
- Orgeira, José Luis
- Orghidan, T
- Orghidan, Traian
- Orgren, M C Ferreira
- Orgussaar, Getriin
- Orhant, Georges E R J
- Oriani, A
- Oriani, Aldo
- Oriani, Aline
- Orians, Gordon H.
- Orias, Oscar
- Orico, Lilian Dias
- Oriental Bird Club.
- Oriental Importing Company.
- Oriental Seed Co.
- Oriental Seed Company.
- Origer, Thomas M.
- Orihara , Takamichi
- Orihara, Takamichi
- Oring, Lewis W
- Orinoco Nurseries.
- Oriole, Golden
- Orionte, Enrique
- O'Riordan, Ruth
- Oristanio Vaz de Lima, Patricia
- Orivel, Jerome
- Orjuela-Rojas, Alianis M.
- Orkin, P. A.
- Orkney Natural History Society.
- Orla-Jensen, S. (Sigurd), 1870-1949
- Orlandi, Patrícia Puccinelli
- Orlandin, E.
- Orlandini, Priscila
- Orlando J. Smith (Firm)
- Orlando Nurseries.
- Orlando, Luis
- Orlando, P A R K
- Orlando, T.
- Orlando, TC.
- Orlando, Tereza Cristina
- Orlando-Guerrero, IJ
- Orlandoni, M. J.
- Orleans County Society of Natural Sciences.
- Orléans, Henri Philippe Marie, Prince d', 1867-1901
- Orleans, Louis Philippe Robert, duc d', 1869-1926
- Orléans, Philippe, duc d', 1674-1723
- Orlov, Alexei
- Orlov, Alexey
- Orlov, Igor
- Orlov, Nikolai L.
- Orlov, Victor
- Orlov, Victor N.
- Orlova-Bienkowskaja, Marina J
- Orlović, Saša
- Orlovich, D
- Orlovskaya, E R
- Orlovskytė, Svetlana
- Ormathwaite, John Benn Walsh, Baron, 1798-1881
- Orme, Andrew
- Orme, Andrew E
- Orme, W J
- Ormerod, E. A.
- Ormerod, Edward Latham, 1819-1873
- Ormerod, Eleanor (Eleanor Anne), 1828-1901
- Ormerod, Eleanor A. (Eleanor Anne), 1828-1901
- Ormerod, Eleanor Anne.
- Ormerod, Paul
- Ormerod, Paul
- Ormerod, Paul
- Ormerod, S J
- Orme-Smith, C.
- Ormiston, Allen R
- Ormiston, W.
- Ormond, Carlos Gustavo A
- Ormond, Wilma T
- Ormond, Wilma Teixeira
- Ormsbee, C C
- Ormsbee, Richard A
- Ormsby, B
- Ornamental Nurseries.
- Ornamental Nursery (Saint James City, Fla.)
- Ornamental Nursery Company.
- Ornat, Arturo Lopez
- Orndorff, William D
- Orndorff, William Ridgely
- Ornduff, Robert
- Ornelas García, C. Patricia
- Ornelas, Elysse
- Ornelas, Juan Francisco
- Ornelas, Patricia
- Ornelas-García, Claudia Patricia
- Ornelas-Paz, José de Jesús
- Ornithological Society of the Middle East.
- Ornithological Society of Turkey.
- Ornithologische Gesellschaft in Bayern.
- Ornithologischer Verein in Wien.
- Ornithologischer Verein München.
- Ornstein, Norma
- Oro, D
- Orobio Riofrío, Bernardo
- Orock, Elizabeth
- Orok, Etim Jonathan.
- O'Roke, Earl C. 1887-1958
- Orol Ledden & Son.
- Orol Ledden & Sons.
- Oromi, Pedro
- Oromí, Pedro
- Orona-Castro, F
- Orono, Eugenia Salas
- Oroño, Luis E.
- Oronogo Flower Gardens.
- Oropeza Oropeza, Anastacio
- Oropeza, A.
- Oropeza-Cabrera, Azucena
- Oros-Ortega, Iván
- Oróstica, Mauricio H
- Orosz, Andras
- Orosz, Paul J.
- O'Rourke, A. Desmond (Andrew Desmond), 1938-
- O'Rourke, Charles H.
- O'Rourke, James T.
- Orourke, M E
- O'Rourke, Matthew B
- Orousset, Jean
- Orozco Dávila, Dina
- Orozco Pardo, Clara Inés.
- Orozco Terwengel, Pablo
- Orozco- Vidal, J
- Orozco, Albert
- Orozco, Carlos
- Orozco, Carlos Alberto
- Orozco, Jesus