Janaki Ammal was born on November 4, 1897, in Tellichery, Kerala. Her father was Dewan Bahadur Edavalath Kakkat Krishnan, sub-judge of the Madras Presidency. Her mother, Devi (1864-1941) was the daughter of John Child Hannyngton and Kunchi Kurumbi. She had six brothers and five sisters. In her family, girls were encouraged to engage in intellectual pursuits and in the fine arts, but Ammal chose to study botany.
After schooling in Tellichery, she moved to Madras where she obtained the bachelor's degree from Queen Mary's College, and an honours degree in botany from Presidency College in 1921.She later taught Under the influence of teachers at the Presidency College, Janaki Ammal acquired a passion for cytogenetics
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.
After Janaki's doctorate Janaki returned to India to take up a post as Professor of Botany at the Maharaja's College of Science, Trivandrum, and taught there from 1932 to 1934. From 1934 to 1939 she worked as a geneticist at the Sugarcane Breeding Institute, Coimbatore along with Charles Alfred Barber. Her work during these years included cytogenetic analysis of Saccharum spontaneum as well as generation of several intergeneric crosses such as Saccharum x Zea, Saccharum x Sorghum. Ammal's work at the Institute on the cytogenetics of Saccharum officinarum (sugarcane) and interspecific and intergeneric hybrids involving sugarcane and related grass species and genera such as [Bamboo] (bambusa) were epochal.
From 1940 to 1945 Janaki worked as Assistant Cytologist at the John Innes Horticultural Institution in London, and as cytologist at the Royal Horticultural Society at Wisley from 1945 to 1951. On the invitation of Jawaharlal Nehru, she returned to India in 1951 to reorganise the Botanical Survey of India (BSI).She was appointed as Officer on Special Duty to the BSI on 14 October 1952.
