Remembering Donald J. Armstrong (1937–2019)

We pay tribute to Donald J. Armstrong, who passed away at age 82 on June 13, 2019 in Corvallis, Oregon, USA. He was both an excellent teacher and a respected scientist. His research spanned more than 40 years and ranged from studying cytokinin structure and activity, to secondary metabolism, to inhibition of seed germination. He is fondly remembered by his colleagues, fellow scientists and students for his mentorship, friendship and, above all, as a gentle and kind human being. This tribute draws heavily from an autobiographical note prepared by Donald Armstrong himself for his family and friends, and information shared by his colleagues at Oregon State University.