Happy Birthday, Alfred Rehder
September 4, 2015 marks the 152nd birthday of Alfred Rehder, a pioneering scholar of horticulture, taxonomy (classification of species), and dendrology (study of trees). We invite you to join us in celebrating his rich life and myriad accomplishments.
Alfred Rehder (1863-1949) was born in Germany to a family of horticulturists. After attending Gymnasium, he apprenticed to his father and later continued his botanical studies in Berlin. There he worked as a gardener and in 1895 became the associate editor of Moller’s Deutsches Gartner-Zeitung. He published over a hundred articles during the three years he was associated with the magazine. In 1898 at age 34, Rehder sailed for the United States to undertake dendrological studies for Moller’s and to investigate fruit growing and viniculture in the United States for the German government. To supplement his stipend from Moller’s, Rehder applied to Charles Sprague Sargent to work on the Arboretum grounds for the princely sum of $1.00 a day. As noted in Arnoldia in 1938, “his first task was to eliminate the weeds in the then newly established shrub collection by the vigorous use of a hoe.” Sargent, impressed by his botanical knowledge and work ethic, convinced Rehder to join the Arboretum staff. One of his first assignments was to work on the Bradley Bibliography, a massive listing of all the written works on woody plants published before 1900. The research and publication of the bibliography was funded by Abby A. Bradley as a memorial to her father, William Lambert Bradley (1826-1894) an innovator in the field of chemical fertilizers. By the time it was completed, Rehder had compiled more than 100,000 entries.
Having attended the International Botanical Congress of 1905 in Vienna on behalf of Harvard University, he married Anneliese Hedwig Schrefeld (1875-1967) in Dresden in 1906. The Rehders had three children; Harald Alfred (1907-1996), Gerhard Oskar (1908-1996), and Sylvia Sophie (1912-1996).
Ernest Wilson’s plant collections in China stimulated years of work on the part of Arboretum staff members, not the least being Alfred Rehder. Along with identifying and naming new plants, Rehder collaborated with Wilson to write the Plantae Wilsoniae which documented Wilson’s Chinese plant collections. In 1913 he was awarded an honorary Master of Arts degree from Harvard University for his work on the Bradley Bibliography, and in 1918 he became the Curator of the Herbarium at the Arnold Arboretum. Over the course of his career, Rehder authored some 1,400 plant names and published more than 1,000 articles—in both English and German—in botanical and horticultural publications. His botanical legacy is significant—over sixty genera and species bear his name, including many growing in the Arboretum’s living collections like Ostrya rehderiana, a Chinese tree critically endangered in the wild.
Alfred Rehder officially retired in 1940 at age 77, but continued to work on the immense Bibliography of Cultivated Trees and Shrubs Hardy in the Cooler Temperate Regions of the Northern Hemisphere, published in 1949.
Alfred Rehder’s passion was dendrology, the study of trees. His friend J.T.P. Bijhouwer perhaps described him best when he said, “Others furnished more or less extensive contributions but only Rehder gave his whole soul and his whole life time to dendrological work.”
Rehder’s quotations about trees
“I am glad to learn that you have been successful and have collected many interesting things and taken a lot of photographs. I am particularly interested to see your cherry collection … [i]n a country like Japan where most of the land is under cultivation, many plants once widely distributed have been nearly exterminated and can be found now only in a few less accessible regions … I am very anxious to see the collections you made in Japan; I am sure they will be splendid and highly interesting and valuable.”
Letter to Ernest Henry Wilson during his first expedition to Japan for the Arnold Arboretum, October 12, 1914
“He was a born plant collector; endowed with a strong physique, robust health, indomitable will power and a deep love of plants he succeeded in collecting and introducing into cultivation a greater number of plants than any other collector.”
Memorializing Wilson, Journal of the Arnold Arboretum, October 1930
“[There are] many other factors besides winter temperature which influence the hardiness and growth of certain plants, such as soil, its physical as well as chemical composition, exposure, rainfall, humidity, air drainage and shelter from cold winds. As a rule, one may say that plants stand cold better in a drier situation than in a wet one and that deciduous trees and shrubs generally do well in more exposed situations and in a climate with higher summer temperature, while evergreen plants prefer a sheltered situation and respond to a more humid climate with less extreme summer and winter temperatures; for this reason many deciduous species grow best in the East, while evergreen plants and particularly broad-leaved evergreens thrive better on the northern Pacific coast. In the case of many rarer trees and shrubs hardy at the Arnold Arboretum, owing to lack of tests farther north and farther south, the limits of hardiness are not well known and had to be deduced from their behavior under approximately similar conditions in Europe.”
Introduction, Manual of Cultivated Trees and Shrubs Hardy in North America, 1927
Did you know?
Rehder created the first system of isothermic plant hardiness zones in North America, first published in Manual of Cultivated Trees and Shrubs Hardy in North America.
Early in his employment, Rehder was sent on book-buying trips to Europe for the Arnold Arboretum Horticultural Library.
Throughout his life, Rehder was actively involved in professional societies and organizations on both continents, served as an important connection between colleagues in Europe and the United States, often passing information or requests across the Atlantic.
Arboretum Horticultural Library Holdings
Rehder, Alfred, 1863-1949. The Bradley bibliography : a guide to the literature of the woody plants of the world published before the beginning of the twentieth century. Koenigstein, W. Ger. : Otto Koeltz Science Publishers, 1976.
Rehder, Alfred, 1863-1949. Bibliography of cultivated trees and shrubs, hardy in the cooler temperate regions of the Northern Hemisphere. Jamaica Plain, Mass. : Arnold Arboretum of Harvard Univ., 1949.
Rehder, Alfred, 1863-1949. “Charles Sprague Sargent,” Journal of the Arnold Arboretum. vol. VIII, [Lancaster, Pa. : Arnold Arboretum, 1927]
Rehder, Alfred, 1863-1949. “Enumeration of the ligneous plants of northern China … pt. 1-3.” [Journal of the Arnold Arboretum. vol. iv, pp. 118-192; vol. v. pp. 137-224. vol. vii. pp. 151-227. vol. xiii pp. 385-409. Part 4, Additions and continuation. Cambridge, Mass., 1923-26]
Rehder, Alfred, 1863-1949. Manual of cultivated trees and shrubs hardy in North America : exclusive of the subtropical and warmer temperate regions. Portland, Or. : Dioscorides Press, 
Wilson, Ernest Henry, 1876-1930 and Rehder, Alfred, 1863-1949. A monograph of azaleas : Rhododendron subgenus Anthodendron. Sakonnet, R.I. : Theophrastus Publishers, 1977.
Rehder, Alfred, 1863-1949. “Synopsis of the genus Lonicera.” Issued October 8, 1903. [St. Louis, Mo.] 1903. From the Fourteenth annual report of the Missouri Botanical Garden.
A complete bibliography of Rehder’s works can be found at the end of Clarence E. Kobuski’s obituary in Journal of the Arnold Arboretum, January 1950.