Alfred Rehder sailed for America on the Cunard steamship Cephalonia in the spring of 1898. He had a small stipend from the gardening journal he worked for, Möllers Deutsche Gärtner-Zeitung, to gather material for articles. To supplement his income, Rehder applied to Charles Sprague Sargent, director of the Arnold Arboretum, for summer employment as a “working student” on the grounds. He was put to work weeding the newly planted shrub collection “by the vigorous use of the hoe,” as he later recalled, his labors earning him the princely sum of $1.00 per day. Rehder had planned to return to Germany in the fall but Sargent, recognizing his potential value to the institution, convinced him to stay in Boston as an assistant in the Arboretum’s herbarium.

Rehder’s first major assignment came by way of Charles E. Faxon, curator of the herbarium and illustrator of Sargent’s Silva of North America. Faxon had been approached by Liberty Hyde Bailey of Cornell University to prepare drawings for his Cyclopedia of American Horticulture. Faxon, who was busy with other projects, delegated this request to Alfred Rehder, who sent Bailey some illustrations as well as an article on Aesculus with a note explaining that his talents were better suited to writing than to drawing. Bailey was impressed by Rehder’s work and had him write all the material on woody plants for the Cyclopedia, an assignment which took him over a year to complete. Rehder traveled to Europe for three months in the summer of 1901 to complete research for his monograph, Synopsis of the Genus Lonicera. There he studied specimens of honeysuckles—living plants and dried herbarium specimens—and began work on his next project, the Bradley Bibliography.

In 1900, Charles Sargent selected Rehder to compile the Bradley Bibliography. This five volume, 3,789-page work is “a guide to the literature of woody plants, including books and articles in the proceedings of learned societies and in scientific and popular journals, published in all languages to the end of the nineteenth century.” Partial funding for its creation came from a gift by Abby A. Bradley in memory of her father William Lambert Bradley of Hingham, Massachusetts, who died in 1894. Bradley, who made his fortune in the chemical fertilizer industry, was devoted to the study of trees, and his daughter’s gift was to promote the scientific activities of the Arboretum. Sargent decided that the donation would be best used to create a comprehensive and up-to-date bibliography of woody plants, which would in turn facilitate research activities by the staff. The assignment before Rehder was monumental, and to complete it he consulted every botanical library collection in the eastern United States, as well as making two trips to Europe to visit libraries in ten countries. He also employed consultants who sent additions to the Bradley Bibliography for material in languages in which he was not adept, such as Hungarian and Serbian. In the bibliography, the entries for publications that Rehder did not examine himself are marked with a small symbol, but those total fewer than five percent of the more than 100,000 entries. The first volume was published in 1911 with a further four volumes being issued through 1918. His work did not go unnoticed: Harvard University awarded Rehder an honorary Master of Arts degree in 1913 for his work on the Bradley Bibliography.

Rehder and Wilson

Rehder continued his compilation of the Bradley Bibliography through the publication of the first volume in 1911 and beyond for those remaining, but as herbarium assistant he also worked to identify the huge number of specimens brought back from China by Ernest H. Wilson on his 1907–1909 and 1910–1911 collecting trips. The 1907–1909 expedition alone produced over 50,000 herbarium sheets, and seeds, cuttings, bulbs, and roots of over 1,000 species, some of them completely new, and all of which needed identification and classification. The documentation of this labor by Rehder and Wilson, as well as their colleagues George Russell Shaw and Camillo Schneider, was the three-volume Plantae Wilsonianae: An Enumeration of the Woody Plants Collected in Western China for the Arnold Arboretum of Harvard University During the Years 1907, 1908, and 1910 by E. H. Wilson. Rehder and Wilson would also collaborate on A Monograph on Azaleas, published in 1921, as well as a number of articles in the Journal of the Arnold Arboretum. In addition to their professional collaboration, they and their families were also genuine friends. In his letters to Rehder from Japan, Wilson often sends greetings from his wife Ellen to Rehder’s wife Anneleise, and in a letter to Wilson from Breslau in 1930, Rehder familiarly tells about his having some “good Rhine wine.”

Wilson’s collecting trips to Japan in 1914, and Japan, Korea, and Formosa (Taiwan) in 1917–1919, as well as those of Joseph F. Rock from 1922 to 1927, swelled the herbarium holdings exponentially and provided a seemingly endless stream of plant material for analysis. In a 1926 letter to Elmer D. Merrill (then the Dean of the College of Agriculture at the University of California, Berkeley, and later Director of the Arnold Arboretum) Rehder laments, “Like you I am getting ‘snowed under’ with material coming in all the time.” With the death of Charles Faxon in 1918, Rehder was appointed curator of the herbarium and during his 22-year tenure he increased the holdings by over 300,000 mounted specimens. Many of those sheets were the product of Arboretum-sponsored expeditions such as those by Wilson and Rock, but through his network of colleagues at other institutions, Rehder also actively collected duplicate sets of their sheets to fill gaps in the Arboretum herbarium holdings of the flora of important regions.

Rehder as Writer and Editor

In 1919, Rehder took over the behind-the-scenes management of a new institutional periodical, the Journal of the Arnold Arboretum. He had lobbied for its creation to fill the gap left by the demise of Garden and Forest in 1897 and to provide a quarterly forum for articles more technical and lengthy than could be accommodated by the Bulletin of Popular Information. In his preface to volume one, issue one, Sargent summed up its purpose, “In its pages will appear notes on trees and shrubs with descriptions of new species and their relationships, letters from correspondents, and notes on the vegetation of countries visited by officers and agents of the Arboretum.” While it was Sargent’s name which appeared as editor at that time, the bulk of the production work, preliminary editing, and the authorship of many articles for the Journal fell on Rehder’s shoulders. In 1926, Rehder became joint editor to assist an increasingly frail Charles Sargent. With volume eight the next year, Rehder and Wilson assumed joint editorial control. Wilson’s untimely death in an automobile accident in October 1930 caused more reorganization and Rehder assumed the role of senior editor with Joseph Horace Faull and Karl Sax as associate editors. In the following year Clarence Kobuski, Rehder’s assistant in the herbarium, took over for Sax as joint editor and continued in this role until Rehder’s retirement in 1940. At that time, A. C. Smith became editor as well as curator of the herbarium, and a ten-member editorial board was formed that included Alfred Rehder, who continued in this capacity until 1948, just a year before his death.

Charles Sprague Sargent, who had guided the Arnold Arboretum since its founding in 1872, died in March 1927 after several years of declining health. The institution was on shaky fiscal ground, forcing acting director Ernest Wilson to cut costs wherever he could. He trimmed the staff in Jamaica Plain and abroad, even curtailing Joseph Rock’s plant collecting in western China. But in the midst of the turmoil, publication of Rehder’s Manual of Cultivated Trees and Shrubs Hardy in North America provided a bright spot for the institution in that momentous year. The Manual presented “a systematic and descriptive enumeration of the cultivated trees and shrubs hardy in North America,” and facilitated “their identification by means of analytical keys.” It immediately became the go-to book for botanists and horticulturists alike. The book proved so useful and popular that it went to a second printing. In 1940, a completely revised second edition was issued, which took in new species and applied changes to rules and nomenclature adopted in the 1930 and 1935 International Botanical Congresses. Multiple reprintings of this second edition of the Manual have been made over the years, including a paperback version as recently as 2001. In the foreword to a commemorative 1986 reprinting of the Manual, botanist Theodore Dudley noted that Rehder “possessed an insatiable curiosity and outstanding originality, demanded of himself the very highest standards, and was dedicated to the systematics and biology of all woody plants.”

Rehder’s Legacy

Alfred Rehder was well respected by his colleagues at the Arboretum and elsewhere, and by all accounts was also extremely well liked by everyone who knew him. He was a mentor to many of the younger Arboretum staff; his assistant in the herbarium, Clarence Kobuski, considered it a privilege to have worked with him and remembered him as even-tempered and fatherly. Outside of work, Rehder was a cultured man who had especially enjoyed attending the opera when he lived in Germany, but who also delighted in tending his garden and caring for the wild birds which came to his feeders and birdbath.

The year 1940 marked Rehder’s seventy-seventh birthday and the maximum age he could continue to work for Harvard University. He reluctantly retired from the Arboretum but retained an office for his use in the Hunnewell Building where he filled his time with a final great project, the Bibliography of Cultivated Trees and Shrubs, Hardy in the Cooler Temperate Regions of the Northern Hemisphere. It “assembled the accepted names, with synonyms, of all the entities treated in his Manual,” and then provided citations in the botanical literature for those names. It was a project long in the making; Rehder had been assembling a card catalog since 1915 of references for use in the Bibliography. By the time he got around to writing it there were nearly 150,000 cards of citations. Rehder completed and saw the book to press in June 1949. In July 1949 he died quietly at his home on Orchard Street, in Jamaica Plain, just steps from the Arnold Arboretum where he had spent more than half a century. He left an extensive botanical library which, with the help of Elmer D. Merrill, his family sold to the National Museum in Manila whose library and collections had been destroyed in the Second World War.

Citation: Pearson, L. 2013. Remembering Alfred Rheder. Arnoldia, 71(2): 18–24.

Alfred Rehder’s career was no doubt aided by his immigration to the United States, where, with hard work and intelligence, he could make a name for himself professionally despite the lack of a university degree. Rehder also happened to be in the right place at the right time; his arrival coincided with an increasing institutional interest in Asian plant exploration. His depth of knowledge and attention to detail were recognized and would prove invaluable for the growth of the Arnold Arboretum through the first half of the twentieth century.


Anonymous. 1938. Notes. Bulletin of Popular Information, Series 4, 6(11): 69.

Anonymous. 1938. A Tribute to an Eminent Botanist. Bulletin of Popular Information, Series 4, 6(2): 14.

Anonymous. 1940. Professor Rehder’s Retirement. Bulletin of Popular Information, Series 4, 8(11): 57–60.

Kobuski, C. E. 1950. Alfred Rehder, 1863–1949. Journal of the Arnold Arboretum 31(1): 1–38.

Rehder, A. 1903 Synopsis of the genus Lonicera in: Fourteenth annual report of the Missouri Botanical Garden. pp. 27–232.

Rehder, A. 1949. Bibliography of cultivated trees and shrubs, hardy in the cooler temperate regions of the Northern Hemisphere. Jamaica Plain, Mass.: Arnold Arboretum of Harvard University.

Rehder, G. 1972. The Making of a Botanist. Arnoldia 32(4): 141–156.

Wyman, D. 1940. A Hardiness Zone Map for the United States. Bulletin of Popular Information, Series 4, 8(12): 61–64.

Wyman, D. 1967. Plant Hardiness Zone Maps. Arnoldia 27(6): 53–56.

Archival items

“Alfred Rehder 1863–1949,” an essay by J.T.P. Bijhouwer.

“Prof. Rehder, Noted World Botanist, Dies.” July 22, 1949. An obituary from an unidentified newspaper.

“Sought Rare Books 10 Years,” July 9, 1911. An article from an unidentified newspaper announcing the publication of the Bradley Bibliography.

Lisa Pearson is Head of Library and Archives at the Arnold Arboretum.