Stearn received many honours for his work, at home and abroad, and was made a Commander of the Order of the British Empire (CBE) in 1997. Considered one of the most eminent British botanists of his time, he is remembered by an essay prize in his name from the Society for the History of Natural History, and a named cultivar of Epimedium, one of many genera he produced monographs on. He is the botanical authority for over 400 plants that he named and described.