Emery was born on June 9, 1892, in Champaign, Illinois. He graduated from Lawrenceville High School in 1911 and completed a BA degree at Wittenberg College in 1915 and an MA degree at Ohio State College in 1916.
He joined the Division of Plants at the National Museum in January 1918, and was in military service from 1918 to 1919. He collected local flora from 1918 to 1924, and began collecting in Haiti with W. L. Abbot, January-July 1920, returning several times in 1925-26 and 1928-29. His specialty was the family Acanthaceae. He published nearly 500 new species in this family. About 30 species are named for him, mostly from Haiti.
Emery died in 1968.
He was elected to the Washington Biologists’ Field Club in 1924 and was awarded an honorary member in 1963.