- Thorburn, Archibald, 1860-1935
- Thorburn, Dean C.
- Thorburn, Dean C.
- Thorburn, Edwin B.
- Thorburn, Grant, 1773-1863
- Thorburn, J. M., & co., New York.
- Thorburn, J.M. & Co.
- Thoreau Museum Of Natural History (Middlesex School (Concord, Mass.))
- Thoreau, Henry David, 1817-1862
- Thoreau, Sophia E.,
- Thorel, Clovis, 1833-1911
- Thorel, Octave Émile Florent
- Thorell, T. (Tord), 1830-1901
- Thorington, Glyne U.
- Thorington, J. Monroe (James Monroe), 1894-
- Thorington, Richard W.
- Thorius, Raphael, 1625
- Thorley, John, 1671-1759
- Thorley, John.
- Thormanby
- Thormann, Birthe
- Thormann, Jana
- Thormeyer, Gottlob Friedrich, 1775-1842
- Thormin, Terry W.
- Thorn, A.
- Thorn, Bruce G
- Thorn, Erik
- Thorn, K. M.
- Thorn, Kailah M.
- Thorn, L. B.
- Thorn, Percy F.
- Thorn, R
- Thorn, R. Greg
- Thorn, S.
- Thornback, Jane.
- Thornber, J. J. (John James), 1872-1962
- Thornber, Walter S.
- Thornburg, Ashley A.
- Thornburg, David C.
- Thornburgh, Dale A.
- Thornburrow, Danny
- Thornbury, David Walter, 1948-
- Thornbury, Frank J
- Thorndale Farm,
- Thorndike, Albert
- Thorndike, Edward H.,
- Thorndike, Edward L. (Edward Lee), 1874-1949
- Thorndike, Lynn, 1882-1965
- Thorndike, Townsend W.
- Thorndyke, Michael C.
- Thorne, Barbara L.
- Thorne, Chas. E. (Charles Embree), 1846-1936
- Thorne, Edwin
- Thorne, Fred
- Thorne, Gerald, 1890-1975
- Thorne, H. R.
- Thorne, Harry W.
- Thorne, J. Frederic,
- Thorne, James H
- Thorne, Joan
- Thorne, John. H.
- Thorne, K. H.
- Thorne, Kaye Hugie
- Thorne, Larry Martin.
- Thorne, Leigh
- Thorne, Linda
- Thorne, M. J.
- Thorne, Nicholas
- Thorne, Robert F.
- Thorne, Robert, 1527
- Thorne-Correia Expedition (1928-1929)
- Thornely, Laura Roscoe
- Thorner, Melvin W
- Thornham, Dan
- Thornhill, Alan D.
- Thornhill, Albert R.
- Thornhill, John
- Thornhill, Mark
- Thornhill, Robert W
- Thornless Cactus Farming Company.
- Thornley, Gertrude
- Thornlodge Farms
- Thornn, Helgason
- Thornthwaite, C. W. (Charles Warren), 1899-1963
- Thornton, A. W. (Augustus Willoughby), 1833-
- Thornton, Bob
- Thornton, Edward Bennett.
- Thornton, Edward C.,
- Thornton, Elysia
- Thornton, H
- Thornton, I. W. B. (Ian W. B.)
- Thornton, Ian
- Thornton, Philip L.
- Thornton, Polly
- Thornton, R. C.
- Thornton, Robert John, 1837
- Thornton, Robert John, 1768?-1837
- Thornton, T. O.
- Thornton, Thomas F
- Thornton, Thomas, 1757-1823
- Thornton, Thomas.
- Thorogood, Chris
- Thorogood, Ed
- Thorold Rogers, James E
- Thoroughgood Strawberry Plant Farm.
- Thorp & Adams Mfg. Co.
- Thorp, Corey J.
- Thorp, J. K. R.
- Thorp, James H.
- Thorp, James.
- Thorp, Robbin W
- Thorp, Robbin W., 1933-
- Thorpe, A G
- Thorpe, Alan
- Thorpe, Charles.
- Thorpe, Francis Newton, 1857-1926
- Thorpe, Fred
- Thorpe, Heather G
- Thorpe, J.
- Thorpe, James, 1876-1949
- Thorpe, Jeffrey.
- Thorpe, John M., 1932-$ive
- Thorpe, John P.
- Thorpe, Kevin W.
- Thorpe, Laura A.
- Thorpe, Malcolm Rutherford, 1891-
- Thorpe, Michael
- Thorpe, R. S. (Roger S.)
- Thorpe, Roger
- Thorpe, S. E.
- Thorpe, Spencer R
- Thorpe, Stanley.
- Thorpe, T. E.
- Thorpe, T. E., Sir, (Thomas Edward), 1845-1925
- Thorpe, T. E.; Morton, E.H.
- Thorpe, Thomas Bangs, 1815-1878
- Thorpe, V G
- Thorpe, V. Gunson
- Thorpe, W. H.
- Thorpe, William Walford
- Thorrold, Simon R.
- Thorsell, James
- Thorsen, Mike
- Thorson, Lee C.
- Thorson, Thomas B., 1917-1995
- Thorstad, Eva B.
- Thorstrom, Russell
- Thorud, David B.
- Thorup, Kasper
- Thory, Claude-Antoine, 1759-1827
- Thos. A. McBeth (Firm)
- Thos. D. Miller (Firm)
- Thos. Griswold & Co.
- Thos. Jackson (Nursery : New York, N.Y.)
- Thos. Jackson (Nursery : Portland, Me.)
- Thos. L. Galvin (Firm)
- Thos. Rogers & Sons Nurseries.
- Thos. Rogers & Sons.
- Thos. W. Emerson Co.
- Thothathri, K.
- Thouin, André, 1747-1824
- Thouin, Gabriel, 1747-1829
- Thoulet, J. (Julien), 1843-1936
- Thousand Flowers.
- Thouvenin, Maurice-François, 1857-
- Thouvenot, Louis
- Thouverez, Emile, 1862-
- Thrailkill, James A
- Thrale, Richard, active 1650-1667
- Thrall, Peter H
- Thrän, Daniela
- Thrasher, Halsey, pseud.
- Thrasher, J. S. (John Sidney), 1817-1879
- Threadgill, Paul F.
- Threatful, David L.
- Three anglers, pseud.
- Three Laurels (Nursery)
- Three Point Gardens.
- Three Sisters Golf Resorts Inc.
- Three Springs Fisheries.
- Threlfall, Miranda E.
- Threlfall, Richard
- Threlfall, Susan
- Threlfall, Timothy J
- Threlfall, Timothy J.
- Threlfall, William
- Threlkeld, John L.
- Threlkeld, William Logan, 1893-
- Threloff, Doug L.
- Throne, Alvin L.
- Throne, James E.
- Throop, Emilie
- Throop, James A.
- Throssell, Terrence.
- Thrower, Stella L
- Thrum, Thomas George 1842-1932
- Thrupp, G. A.
- Thrush, Mark
- Thuau, veuve,
- Thuau, C.,
- Thudichum, J. L. W. (John Louis William), 1829-1901
- Thuesen, Erik V.
- Thuet, P.
- Thuiller, Wilfried
- Thuillier, Henry Edward Landor
- Thuillier, Jean Louis, 1757-1822
- Thukral, A. K.
- Thulajappa, Y.
- Thulborn, Tony
- Thulin, Carl- Gustaf
- Thulin, Gustav
- Thulin, Mats, 1948-
- Thull, M.
- Thullbery, Howard A.,
- Thullen, J. S.
- Thumb Nursery.
- Thümen, Felix von, 1839-1892
- Thumlert, T. A.
- Thumma, Harry O.
- Thumser, Nina N
- Thunberg, Carl Peter, 1743-1828
- Thunell, Robert
- Thünen, Johann Heinrich von, 1783-1850
- Thunen, Robert L.
- Thunhikorn, Somying
- Thupa, Raúl
- Thura, Myint Kyaw
- Thurab, Franklin.
- Thurant, Joannes-Baptista.
- Thurau, Friedrich, 1843-1913
- Thurber, Charles Herbert.
- Thurber, David L.
- Thurber, E. C.
- Thurber, E. Carleton.
- Thurber, Francis Beatty, 1842-1907
- Thurber, Gary D.
- Thurber, George, 1821-1890
- Thurber, Hartford G.
- Thurber, Joanne M.
- Thurber, Lorne A.
- Thurber, William R.
- Thurburn, Roberta
- Thureau, Gustav
- Thuret, Gustave, 1817-1875
- Thurgate, Nicole Y
- Thurgauische Naturforschende Gesellschaft
- Thurgood, Denis
- Thurgood, Elizabeth
- Thüringische Botanische Gesellschaft.
- Thurlbourn, William, 1768