Professor Paul Hadley of the University of Reading's School of Biological Sciences picked up the prize, which is sponsored by the Marsh Christian Trust in conjunction with the RHS, for his outstanding contribution to horticulture.
Much of his work has focused on research relating to fruit and vegetable production and his studies have led to the development of mathematical models that have helped growers predict the responses of crops to their environment.
Hadley has also helped supervise some 40 PhD students and in 2008 he took on responsibility, along with Professor Nick Battey, for the management and curation of the National Fruit Collection at Brogdale - one of the largest fruit collections in the world.
He is also heavily involved in research on cocoa and has just begun a new five-year study on the effects of climate change on cocoa. He has recently been elected chair of the next International Cocoa Conference, to be held in 2013.
Simon Thornton-Wood, director of science and learning at the RHS, commented: "Paul won the award because of his significant contribution to horticulture, demonstrated by his enthusiasm, energy, efforts at education and research excellence."
Professor Gavin Brooks, head of the University of Reading's School of Biological Sciences, added: "The school is delighted that Paul's significant contributions to the crop production research area have been recognised by the Marsh Award.
"At a time when the future of food security and crop production is so important, we are very fortunate to have Paul as a leading expert in this field". Hadley was presented with the prize at the RHS Annual Awards on 15 February.