Carleton was born on June 12, 1873, in Little Rock, Iowa. He attended college in Ames, Iowa, and received a BS degree in 1896, an MS degree in 1899, and a DSc degree hon. causa in 1920. He taught botany there from 1896 to 1898 when he joined the U.S. Department of Agriculture Division of Agrostology. There he initiated experiments in grain sorghums and broom corn, classified and named wheat varieties from 1914 to 1918, and was in charge of the Division of Cereal Crops and Diseases of the U.S. Department of Agriculture from 1918 to 1929. He specialized in the willows (genus Salix).
Carleton was a member of many scientific organizations, including the Southern Appalachian Botanical Club. He was secretary (1910-14) and president (1916) of the Agronomy Society, and Treasurer (1905) and vice-president (1919) of the Botanical Society of America.
Carleton was a member and executive secretary of U.S. Department of Agriculture correlation committees working with the Tennessee Valley Authority and the Southern Association of Land Grant Colleges. Carleton was forever an advocate of better Federal State cooperation.
He died on February 2, 1958, at the age of 84 in Washington, D.C. The death of Carleton brought to an end a lifetime of service to his country and to his friends. His accomplishments as botanist, cerealist, agronomist, and administrative coordinator on many executive committees were well known by his contemporaries.
He was elected to the Washington Biologists’ Field Club in 1901 and terminated membership in 1907.