He was born in Newton, Massachusetts. His parents were Levi Thaxter and the poet Celia Thaxter. After receiving a Harvard education and securing his Ph.D. there, in 1888 he became a professor of biology and botany in the university. He was known for his work on the fungal group, the Laboulbeniales, and published many individual papers and a huge five volume work on the subject. Thaxter served as editor of the journal Annals of Botany from 1907 to 1932. He was elected a foreign member of the Russian Mycological Society, Linnean Societies of London and Lyon, Royal Swedish Academy of Sciences, Royal Academy of Denmark, Botanical Society of Edinburgh, Academy of Science of the Institute of France, British Mycological Society, and Deutsche Botanish Gesellschaft. He received the Prix Desmazières for 1902 from the French Academy for his work on Laboulbeniales. In the United States Thaxter was elected to the American Academy of Arts and Sciences, the American Philosophical Society, and the National Academy of Sciences (Clinton, 1935).