- Oppong-Mensah, Birgitta
- Opran, Robert
- Oprasertsawat, Panut
- Oprea, Adrian
- Oprea, M.
- Oprea, Monik
- Oprecht, E
- Opresko, D M
- Opresko, D M
- Opresko, Dennis
- Opresko, Dennis M
- Opršal, Zdeněk
- Opstaele, Marc van
- Opytnoe pole (Odesa, Ukraine)
- Oquendo, Oviana
- O'quinn, Robin
- Oquossoc Angling Association.
- Orabi, Gamal M
- Oradovskaya, M M
- Oraie, Hamzeh
- Oral, Münevver
- Oram, D A
- Oram, Keith
- Oram, Ryan
- Orams, M B
- Oran, R B
- Oran, R Batur
- Oran, S
- Oran, Seyhan
- Oranday Cárdenas, A
- Oranday, MA
- Oranday-Cárdenas, A.
- Orange County Fern Growers Association.
- Orange County Fern Growers' Association.
- Orange County Nurseries.
- Orange County Nursery and Land Company.
- Orange County Nursery Co. (Anaheim, Calif.)
- Orange County Nursery Co.,
- Orange County Nursery,
- Orange County Ornamental Nursery.
- Orange Hill Nursery and Fruit Orchards.
- Orange Judd & Company.
- Orange, A
- Orange, Paul
- Orantes, Carolina
- Oraze, Michael J
- Orazi, Diego
- Orazio, Christophe
- Orbach, Eylon
- Orbigny, Alcide Dessalines d', 1802-1857
- Orbigny, Charles d', 1806-1876
- Orbigny, H D'
- Orbigny, Henri d' 1845-1915
- Orcan, Nermin
- Orcel, Jean
- Orces V., Gustavo,
- Orces-V, G
- Orchadotte Nurseries.
- Orchard & Garden Supply Company.
- Orchard Hill Nursery.
- Orchard Home Nursery.
- Orchard Nursery,
- Orchard, A E
- Orchard, Ae
- Orchard, Anthony E
- Orchard, F. P.
- Orchard, M. J.
- Orchard, Stan
- Orchard, T A
- Orchard, William C.
- Orchardson, I. Q.
- Orchid Conference South Kensington) 1885-
- Orchid Exchange (Philadelphia, Pa.)
- Orchid Gardens.
- Orchid House
- Orchid Ranch, Inc.,
- Orchid Research Co.,
- Orchid Society of New South Wales.
- Orchidéenne, société d'amateurs d'orchidées.
- Orchids By Turner, Inc.,
- Orchids By Wilson.
- Orchidvale,
- Orchidwood (New Rochelle, N.Y.)
- Orchidwood Gardens.
- Orchidwood, Inc.
- Orchiston, D. W.
- Orchiston, W
- Orchiston, Wayne
- Orchymont, A D
- Orchymont, A D'
- Orci, Kirill
- Orci, Kirill Márk
- Orcival, J
- Orcutt Co. (Orcutt, Calif.)
- Orcutt Seed and Plant Company.
- Orcutt, Alfred Walter.
- Orcutt, Barbara S
- Orcutt, Charles Russell, 1864-1929
- Orcutt, Eliza E.
- Orcutt, I. H.
- Orcutt, Mary Logan
- Orczán, Kund Ákos
- Orczewska, Anna
- Ord, George, 1781-1866
- Ord, Richard E
- Ord, Richard, 1849-1920
- Ord, Richard.
- Ord, W Michael
- Ord, William M. (William Miller), 1834-1902
- Ordano, M
- Ordano, Mariano
- Ordas, Jorge Anton D.
- Ordaz Silva, Salvador
- Orde, C J
- Orde-Browne, Granville St. John, Sir, 1883-1947
- Ordenes, Rodrigo
- Ordenes-Clavería, Rodrigo
- Ordoñez Bautista, Danny Josué
- Ordóñez Ch, María Fernanda
- Ordóñez de Ceballos, Pedro, ca 1545-ca 1630
- Ordoñez Mazier, Diego
- Ordoñez Mazier, Diego Iván
- Ordoñez Trejo, Eduardo Javier
- Ordoñez, Constanza Rubilar
- Ordóñez, Ezequiel, 1867-
- Ordoñez, Mariae
- Ordoñez, Oscar Stiven
- Ordoñez, Reina
- Ordóñez-Delgado, Leonardo
- Ordóñez-García, Magali
- Ordóñez-Garza, Nicté
- Ordóñez-López, Uriel
- Ordoñez-Mazier, Diego I.
- Ordóñez-Prado, Casimiro
- Ordóñez-Reséndiz María Magdalena
- Ordorica Hermosillo, Antonio
- Ordoyno, Thomas.
- Ordoyo, Alea Ester T
- 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
- Orecchia, Simona
- 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, John
- 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, Markku
- Orell, P
- Orell, Peter
- Orellana Carrera, Habibi
- Orellana Liebbe, María Cristina
- Orellana, Daniel
- Orellana, Fernanda I
- Orellana, Flavio
- Orellana, Francisco
- Orellana, Francisco A
- Orellana, José Alfredo Vicente
- Orellana, José I
- Orellana, José I.
- Orellana, K. Samanta
- Orellana, Leonardo Valdés
- 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, J M
- Orensanz, José M
- Orensanz, Juancho
- Orenstein, A. J.,
- Orenstein, Alexander Jeremiah, 1879-
- Orenstein, Ronald I
- Orenstein, Ronald I. (Ronald Isaac), 1946-