Morris grew rare and exotic plants at Benton End, which he collected on expeditions to the Mediterranean and North Africa and in many cases introduced to cultivation in Britain for the first time. He planted them in an idiosyncratic style which admirers have viewed as an extension of his work as a painter: Beth Chatto described the garden as a "bewildering, mind-stretching, eye-widening canvas of colour, textures and shapes". He was most prolific as a cultivator of irises; he grew around 1,000 varieties, and bred up to 90 cultivars of his own. His rose Rosa 'Sir Cedric Morris' and poppy Papaver orientale 'Cedric Morris' are both widely commercially available.
