- Clement I, Pope.
- Clementino dos Santos, Antonio
- Clements, B. W. (Burie Webster), 1927-
- Clements, Charlie
- Clements, D R
- Clements, David
- Clements, David K
- Clements, Edith S. (Edith Schwartz)
- Clements, F A
- Clements, Frederic E. (Frederic Edward), 1874-1945
- Clements, Gopalasamy Reuben
- Clements, J. Morgan (Julius Morgan), 1869-
- Clements, Jeff C
- Clements, Jennie H.,
- Clements, K D
- Clements, Krista L
- Clements, L A
- Clements, Margaret
- Clements, Mark Alwin
- Clements, Nolan
- Clements, S J
- Clements, Sharon J
- Clements, Thomas
- Clements, Thomas 1898-1996
- Clements, V. A. (Victor Albert), 1902-
- Clements, W. G.
- Clemes, William Hall
- Clemesha, Stephen C.
- Clemesha, Steve C
- Clemesha, William Wesley.
- Cleminson, Glen
- Clemmer, Glenn H.
- Clemmer, Pam.
- Clemmer, Paul W. (Paul Wescoe), 1888-
- Clemons, Chad M.
- Clemons, Duffie
- Clemons, Joe E. Jr.
- Clemons, Laurence
- Clench, Harry K.
- Clench, Mary H.
- Clench, William James, 1897-1984
- Clendenen, Gary W.
- Clendenin, Ida
- Clendenning, K A
- Clennell , Lynette
- Clennell, Luke 1781-1840
- Clepper, Henry Edward, 1901-1987
- Clerc, Louis.
- Clerc, P. le.
- Clerc, Philippe
- Clerc, W
- Clerck, Carl (Carl Alexander), 1710-1765
- Clercq, Frederik Sigismund Alexander de, 1842-1906
- Clergé, active 1857-1858
- Clergue, M
- Clergue-Gazeau, M
- Clericuzio, Marco
- Clerjeau, M
- Clerke, Charles, 1741-1779
- Clermont, Thomas Fortescue, Baron, 1815-1887
- Clermont-Tonnerre, AimeĢ-Marie-Gaspard, duc de, 1779-1865
- Clery, Molly
- Clessin, Stephan, 1833-1911
- Cleto Filho, Sérgio Ernani Nogueira
- Cleu., H
- Cleuet, Jean Michel
- Cleva, Régis
- Cleve, Karl
- Cleve, P. T. (Per Teodor), 1840-1905
- Cleve-Euler, Astrid, 1875-
- Cleveland Academy of Natural Science.
- Cleveland Museum of Natural History
- Cleveland Naturalists' Field Club.
- Cleveland Nursery Company.
- Cleveland Nursery.
- Cleveland Seed Co.
- Cleveland Seed Company.
- Cleveland, Carol M.
- Cleveland, Daniel, 1838-1929
- Cleveland, David A
- Cleveland, Frances E., Mrs.
- Cleveland, George B.
- Cleveland, George F
- Cleveland, Grover, 1837-1908
- Cleveland, H. W. S. (Horace William Shaler), 1814-1900
- Cleveland, L R
- Cleveland, Parker
- Cleveland, Treadwell, 1872-
- Clevenger, Anthony P. (Anthony Paul)
- Clevenger, Erie S.
- Clevenger, J. F. (Joseph Franklin), 1874-
- Clevenger, Lewis,
- Clevenger, Lewis, Dr.
- Clevenger, Sarah
- Clevenger'S Garden,
- Clevenger's Iris Garden.
- Clever-Aurora Nursery.
- Cleverly, E I
- Cleverly, W H
- Cleves, W. B.
- Clevinger, J A
- Clevisch, Anton.
- Clewell, A F
- Clewell, Andre F
- Clewett, Jeff F
- Clewing, Catharina
- Clews, E
- Clews, Lukas L
- Cleyer, Andreas
- Cleynenbreugel, Serge van
- Clezar, Leandro
- Clibrans Ltd.
- Cliff Cave WIne Company.
- Cliff Harris' Longview Nursery,
- Cliff, Edward P. (Edward Parley), 1909-1987
- Cliff, Frank S
- Clifford Avenue Gardens and Nurseries.
- Clifford E. White (Firm)
- Clifford S. Kempton & Co.
- Clifford S. Kempton (Firm)
- Clifford, A
- Clifford, Carleton M.
- Clifford, H. T. (Harold Trevor)
- Clifford, Hugh F.
- Clifford, Hugh, 1866-1941
- Clifford, J. B.
- Clifford, John D., 1778?-1820
- Clifford, Penelope
- Clifford, Sara E
- Clifford, W. K.
- Clift, William, 1775-1849
- Clift, William, 1817-
- Clifton College Scientific Society.
- Clifton, Brenda C
- Clifton, Glenn L.
- Clifton, Jon
- Clifton, Kenneth E.
- Clifton, M P
- Clifton, Percy.
- Clifton-Bumpass, Lisa
- Cliftondale Dahlia Gardens.
- Cligny, Adolphe.
- Climer, H. D.
- Climo, F M
- Cline, Andrew Richard
- Cline, E T
- Cline, Gary R.
- Cline, Henry, 1750-1827
- Cline, J. Romulus.
- Cline, L D
- Cline, Richard.
- Clinebell, Richard R
- Clines, Joanna
- Clingham, Elizabeth
- Clingman Nurseries.
- Clingman Nursery & Orchard Co.
- Clingman Nursery and Orchard Co.
- Clingman Nursery.
- Clingman, A. K.
- Clingman, T. L. (Thomas Lanier), 1812-1897
- Clint McDade & Sons.
- Clint, L
- Clinton Falls Nursery Co.
- Clinton Falls Nursery Co. (Owatonna, Minn.)
- Clinton Falls Nursery Company.
- Clinton L. Pedley (Firm)
- Clinton Nurseries (Clinton, Ky.)
- Clinton Nurseries (Clinton, Conn.)
- Clinton, Brook
- Clinton, DeWitt, 1769-1828
- Clinton, Fall Henry
- Clinton, G. P. (George Perkins), 1867-1937
- Clinton, George W. (George William), 1807-1885
- Clinton, Louis Adelbert, 1868-1923
- Clinton, P.
- Clinton-Baker, Henry William, 1865-1935
- Clippel, Joscineia Kelli
- Cliquennois, Nicolas
- Clisby, Kathryn H
- Clissold, Augustus, 1797?-1882
- Clitheroe, Chrystal
- Clitheroe, Crystal-Leigh
- Clitheroe, Kelly
- Clive Henry
- Clive, Harriet Windsor, 1797-1869
- Clobert, Jean
- Clock, Emma Graham
- Clodd, Edward, 1840-1930
- Clode, Peta L
- Clodius, M
- Cloetta, M.
- Clok, Henry.
- Clokey, Ira W. (Ira Waddell), 1878-1950
- Cloney, Richard A.
- Cloquet,
- Clos, Dominique, 1821-1908
- Clos, Enrique C., 1894-1977
- Clos, Jean Antoine.
- Close, B F
- Close, C. P. (Charles Phillip), 1868-1940
- Close, Hayden L
- Close, J C
- Close, P.
- Close, Paul G.
- Closeburn Nurseries,
- Closek, Collin
- Closs, Darcy
- Closs, G A
- Clot, Antoine Barthélemy, 1793-1868
- Clot, Bernard
- Clot-bey, A. B. (Antoine Barthélemy), 1796-1868
- Clothier, George L. (George Lemon)
- Clothier, Robert Waitman, 1871-
- Clottey, Victor Attuquaye
- Cloud Hill Nursery,
- Cloud, William K.
- Cloud-Hughes, Michelle A
- Cloudland Dahlia Farm.
- Cloudsley-Thompson, J. L.
- Clouet, Michel
- Clough, B J
- Clough, Bret
- Clough, C. T. (Charles Thomas), 1852-1916
- Clough, Ernest E.
- Clough, Garrett C.
- Clough, Ray William, 1885-
- Clough, Yann
- Clougherty, John J
- Clouse, Mary E
- Clouse, Ronald M
- Clousier, Jacques-Gabriel, 1804?
- Clouston, Charles
- Clouten, Bree C
- Clouter, F H
- Cloutier, Louise
- Cloutier, Richard
- Cloutier, Tammy
- Clouzot, Henri, 1865-1941
- Clovena Nurseries.
- Clover Leaf Fruit Farm.
- Clover Leaf Nursery.
- Clover, Elzada U
- Clover, P W
- Clover, Phillip W.
- Cloverleaf Nursery.
- Cloverset Flower Farm.
- Clovis and Gage (Firm)
- Clóvis Costa-Silva, Francisco
- Clowes, Catherine
- Clowes, G H A