Walter Tennyson Swingle, a relentless intellect that transformed American pomology

Authors: STOVER, EDDIE; WRIGHT, GLENN - UNIVERSITY OF ARIZONA

Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2018
Publication Date: 4/1/2019
Citation: Stover, E.W., Wright, G. 2019. Walter Tennyson Swingle, a relentless intellect that transformed American pomology. Journal of American Pomological Society. 73:129-138.

Interpretive Summary: In 1993 Walter Tennyson Swingle established a USDA laboratory and began a comprehensive program to breed disease- and frost-resistant citrus. He recognized the need for genetic diversity in crops and the risks of growing them in monocultures. He proposed testing all known wild relatives for disease-resistance and other advantageous traits that could be introduced to improve citrus. This led him into his comprehensive studies of the comparative anatomy and systematics of the orange subfamily. Through this effort he discovered some new species and several new genera: the genus Swinglea and several cultivars were named in his honor. In the citrus crosses he made or directed, he originated several new categories of citrus. He was an early advocate for permanent, living collections of economically important plants and their close relatives. In 1897-98, in collaboration with David Fairchild, he established the USDA's Office of Foreign Seed and Plant Introduction, and new research facilities were set up in Miami. He conducted plant exploration, mainly in countries surrounding the Mediterranean, and among many other accessions introduced date palms, figs, table grapes, and ‘Clementine’ mandarins. In his duties in the USDA section of Seed and Plant Introduction, he received over 2000 plant introductions. After his retirement from the USDA, Swingle moved to Miami in 1943. It was here he completed his treatise on the taxonomy of the citrus subfamily. “Even in his retirement, Swingle inspired a generation of students with his knowledge, curiosity of nature, and insights into plants. His simple advice to students was ‘Look and look, again and again,’ words still relevant today”.

Technical Abstract: Walter Tennyson Swingle grew up outside of Manhattan, Kansas, attended a one-room schoolhouse and had mastered the entire curriculum at the age of nine. He was then exclusively self-taught or tutored by his mother. He was notorious in his passion for botany, and based on observations, made up his own names for plants that were demonstrably different. His formal engagement with science was ignited when he discovered that plant names and taxonomic distinctions could be found in books! He attended classes at Kansas Agricultural College (now KSU) at 15, and when he graduated at 20 he had already published 27 scientific papers in plant pathology, plant breeding and genetics. It was here that he developed his lifelong friendship with David Fairchild. Swingle joined the USDA in 1891, and in July was sent to Florida to investigate diseases in orange trees. He established a USDA laboratory and began a comprehensive program to breed disease- and frost-resistant citrus. He recognized the need for genetic diversity in crops and the risks of growing them in monocultures. He proposed testing all known wild relatives for disease-resistance and other advantageous traits that could be introduced to improve citrus. This led him into his comprehensive studies of the comparative anatomy and systematics of the orange subfamily. Through this effort he discovered some new species and several new genera: the genus Swinglea and several cultivars were named in his honor. In the citrus crosses he made or directed, he originated several new categories of citrus: the tangelos, citranges and citrumelos (now critical as rootstocks), and many other intergeneric hybrids. He was an early advocate for permanent, living collections of economically important plants and their close relatives. In 1897-98, in collaboration with David Fairchild, he established the USDA's Office of Foreign Seed and Plant Introduction, and new research facilities were set up in Miami. He was a champion for ensuring that introduced plants were disease and pest free. He conducted plant exploration, mainly in countries surrounding the Mediterranean, and among many other accessions introduced date palms, figs, table grapes, and ‘Clementine’ mandarins. He also brought in the Blastophaga wasp to pollinate Smyrna-type figs. In his duties in the USDA section of Seed and Plant Introduction, he received over 2000 plant introductions (listed as “donor” in GRIN), but hundreds of accessions in GRIN list Swingle as the collector (among them numerous Citrus, Phoenix, Pistacia, Prunus, and Vitis accessions, but few including ‘Medjool’ date and ‘Clementine’ remain active). After his retirement from the USDA, Swingle moved to Miami in 1943. It was here he completed his treatise on the taxonomy of the citrus subfamily. “Even in his retirement, Swingle inspired a generation of students with his knowledge, curiosity of nature, and insights into plants. His simple advice to students was ‘Look and look, again and again,’ words still relevant today”.