Alfred Rehder was a horticulturist and taxonomist who worked at the Arnold Arboretum of Harvard University

Harvard University

Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

. Rehder was a newspaper writer from Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 who was originally hired as a laborer at the Arnold Arboretum. His talents for horticultural plant taxonomy were soon recognized, however. Early in his employment he was sent to Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 to purchase books for the library at the Arboretum. When the Journal of the Arnold Arboretum was started in 1919, Rehder was co-editor, along with the Arboretum director, Charles Sprague Sargent

Charles Sprague Sargent

Charles Sprague Sargent was an American botanist. He was the first director of the Arnold Arboretum at Harvard University in Boston, Massachusetts and the standard botanical author abbreviation Sarg. is applied to plants he described.-Biography:Sargent was the second son of Henrietta and...

. Rehder produced a new edition of Manual of Cultivated Trees and Shrubs and authored the Bibliography of Cultivated Trees and Shrubs and The Bradley bibliography. He was co-author, with Ernest Henry Wilson

Ernest Henry Wilson

Ernest Henry "Chinese" Wilson , better known as E. H. Wilson, was a notable English plant collector who introduced a large range of about 2000 of Asian plant species to the West; some sixty bear his name.-Career:...

, of Plantae Wilsonianae and A Monograph of Azaleas.

Rehder created the first system of isothermic zones for the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 that related average winter minimum temperatures to the hardiness

Hardiness

Hardiness may refer to:*Psychological resilience, positive capacity of people to cope with stress and catastrophe*Hardiness , the ability of plants to survive adverse growing conditions...

 of specific plants. That system, along with another system developed by Wladimir Köppen

Wladimir Köppen

Wladimir Peter Köppen was a Russian geographer, meteorologist, climatologist and botanist. After studies in St. Petersburg, he spent the bulk of his life and professional career in Germany and Austria...

, are the basis for all of the climate zone maps in use today.