Ammal taught at Women's Christian College, Madras, with a sojourn as a Barbour Scholar at the University of Michigan in the US where she obtained her master's degree in 1925. Returning to India, she continued to teach at the Women's Christian College. She went to Michigan again as the first Oriental Barbour Fellow and obtained her D.Sc. in 1931. Janaki is mentioned among Indian Americans of the Century in an India Currents magazine article published on January 1, 2000, by S.Gopikrishna & Vandana Kumar: "In an age when most women didn't make it past high school, would it be possible for an Indian woman to obtain a Ph.D. at one of America's finest public universities and also make seminal contributions to her field? The Kerala born Ammal was arguably the first woman to obtain a Ph.D. in botany in the U.S. (1931), and remains one of the few Asian women to be conferred a D.Sc. (honoris causa) by her alma mater, the University of Michigan. During her time at Ann Arbor she lived in the Martha Cook Building, an all-female residence hall and worked with Harley Harris Bartlett, Professor at the Department of Botany. She evolved a cross known as "Janaki Brengal", brengal being the Indian name for eggplant. Her Ph.D. thesis titled "Chromosome Studies in Nicandra Physaloides" was published in 1932.