- Harkins, Gordon S.
- Harkleroad, M. F.
- Harkness, A. D.
- Harkness, B
- Harkness, Bernard
- Harkness, H. W. (Harvey Willson), 1821-1901
- Harkness, Robert
- Harkness, Thomas.
- Harkness, William J. K. 1896-1960
- Harkness, William, 1837-1903
- Härkönen, Tero
- Harkrider, J Robert
- Harl, Josef
- Harlan Farms Nursery.
- Harlan P. Kelsey (Firm)
- Harlan P. Kelsey.
- Harlan, Annita
- Harlan, Caleb, 1814-1902
- Harlan, Caleb.
- Harlan, Geo. O. (George O.)
- Harlan, Harold J
- Harlan, Harry V. 1882-1944
- Harlan, Jack R
- Harlan, Richard, 1796-1843
- Harlan., J R
- Harland, Audrey
- Harland, JNO
- Harland, Rex
- Harland, S C
- Harland, T L
- Harlé, Édouard
- Harle, K J
- Harless, Emil
- Harless, Emil.
- Harlett, John Charles.
- Harley T. Peck & Sons.
- Harley T. Peck (Firm)
- Harley, Basil
- Harley, Dan
- Harley, George W. (George Way), 1894-1966
- Harley, George, 1829-1896
- Harley, J E
- Harley, James
- Harley, John P
- Harley, Mike
- Harley, Peter
- Harley, Raymond Mervyn
- Harley, Robert
- Harley, Samantha
- Harley, William, 1830
- Harley, Winifred J
- Harley, Winifred J., 1895-1979
- Harlin, Æstanus Emanuel.
- Härlin, Mikael
- Harling, G
- Harling, George
- Harling, J
- Harling, Rob
- Harloff, Joachim
- Harlow, Chris
- Harlow, Louis K. 1850-1913
- Harlow, Peter
- Harlow, Peter S
- Harlow, R F
- Harlow, Richard C
- Harlow, Richard Cresson.
- Harlow, Richard F
- Harlow, Richard F.
- Harlow, Wm. M.
- Harlowarden Gardens and Greenhouses.
- Harman, A C
- Harman, A L
- Harman, Allan
- Harman, Dan Myers
- Harman, Dennis M.
- Harman, H. C.
- Harman, Henry James
- Harman, M
- Harman, Mary Theresa, 1877-
- Harman, N. Bishop.
- Harman, Pinckney J.
- Harman, R F
- Harman, T W
- Harman, W J
- Harman, W N
- Harmand
- Harmata, A R
- Harmata, Alan R
- Harmata, Peter J.
- Harmel Peony Company (Berlin, Md.)
- Harmelin, J G
- Harmelin, Jean-Georges
- Harmeling, Benjamin R
- Harmelin-Vivien, Mireille L
- Harmer, A S
- Harmer, Aaron M T
- Harmer, Alec S
- Harmer, Frederic William, 1835-1923
- Harmer, G.
- Harmer, S. F. (Sidney Frederic), 1862-1950
- Harmes, Heinrich.
- Harmison, Lowell T.
- Harmon and Harris Company.
- Harmon Nursery.
- Harmon, Daniel Williams, 1778-1843
- Harmon, Frank Nelson, 1895-
- Harmon, J D
- Harmon, Jamie S
- Harmon, Keith W
- Harmon, Liz
- Harmon, Luke J
- Harmon, R W
- Harmon, R. W. (Ralph Winter), 1916-
- Harmon, Roselee
- Harmon, W
- Harmon, W E
- Harmon, Will.
- Harmon, William E
- Harmond, Jesse E. (Jesse Edward), 1906-
- Harms, B
- Harms, Bruno
- Harms, Danilo
- Harms, H. P.
- Harms, Hermann, 1870-1942
- Harms, Karl Hermann
- Harms, Kyle Edward
- Harms, L J
- Harms, Larry J
- Härms, M
- Harms, R H
- Harms, R T
- Harms, Vernon L
- Harms, Volker W.
- Harms, W
- Harmsen, R
- Harmsen, R.
- Harmsen, Rudolf
- Harmston, F C
- Harmston, Fc
- Harmston, Fred C
- Harn, E H
- Harnack, Adolf von, 1851-1930
- Harnack, Marianne von, 1925-
- Harnden Seed Co.
- Harnden, Boyd M.
- Harnden's Seed Store.
- Harner, Mary J
- Harner, Richard F
- Harness, Dix & Co.
- Harney, Barbara A.
- Harniss, Roy O.
- Harnly, Morris Henry
- Haro, Daniel
- Haro, Daniela
- Haro, G.
- Haro, José A.
- Haro, José G
- Haro, Roger J
- Haro-Castellanos Jorge
- Harold B. Higgins (Firm)
- Harold E. Janes (Firm)
- Harold E. Wolfe (Firm),
- Harold Hall Australian Expeditions 1962-1970
- Harold Hornor (Firm)
- Harold Keays Seed Co.
- Harold L. Codner (Firm),
- Harold Lyke (Firm)
- Harold Stearns (Firm)
- Harold, A S
- Harold, Antony S
- Harold, Catherine E., 1957-
- Harold, Edgar von, 1830-1886
- Harold, G
- Harold, Greg
- Harold, K
- Harold, Laura B. (Laura Brink)
- Harold, N
- Harold, St John
- Haron, N W
- Haron, Noorma Wati
- Haro-Preciado, Hugo J
- Harosi, F I
- Hárosi, Ferenc I.
- Haroun, Ricardo
- Haroun, Ricardo J
- Harouna, Abdoulaye
- Harp, Cyrus R
- Harp, James A
- Harpaz, I.
- Harpeck, K.
- Harpel, Judith A
- Harpel, Judith A S
- Harpel, Judith,
- Harper & Brothers,
- Harper Viola Gardens.
- Harper, A B
- Harper, A V
- Harper, A. E.,
- Harper, A. M. (Alexander Maitland), 1926-
- Harper, Alan G.
- Harper, Arthur Frederick Alan
- Harper, B C S
- Harper, C W
- Harper, Charles Alan, 1942-
- Harper, Charles G. (Charles George), 1863-1943
- Harper, Craig A
- Harper, D A T
- Harper, D E
- Harper, Dat
- Harper, David A T
- Harper, E M
- Harper, E T
- Harper, Elizabeth K
- Harper, Elizabeth M
- Harper, Eugene Howard.
- Harper, F
- Harper, F A
- Harper, Francis
- Harper, Francis P. (Francis Perego), 1856?-1932
- Harper, Francis, 1886-1972
- Harper, G H
- Harper, G W
- Harper, J
- Harper, J A
- Harper, J F
- Harper, J T
- Harper, J. N.
- Harper, James Arthur, 1916-
- Harper, John A.
- Harper, John Russell, 1914-1983
- Harper, John,
- Harper, John, F. R. S. S. A.
- Harper, John.
- Harper, K A
- Harper, K T
- Harper, K. T.
- Harper, Kimball T
- Harper, L F
- Harper, L H
- Harper, Lee
- Harper, Lee H
- Harper, Lee H.
- Harper, Liz
- Harper, Merritt W. (Merritt Wesley), 1877-
- Harper, Michael W.
- Harper, P P
- Harper, Pierre-Paul
- Harper, R L
- Harper, R M
- Harper, R W