Recent research and development has investigated the factors influencing apple tree growth, with the ultimate aim of helping apple growers provide the market with fruit which is consistent in quality and which exhibits the features that consumers value, such as firmness, juiciness, colour and appropriate sugar–acid balance. This chapter begins with a review of important aspects of tree growth and development. It then discusses the importance of rootstocks, with an emphasis on the mechanisms and morphological effects of dwarfing. The chapter provides a brief introduction to the manipulation of tree growth and development and follows it up with a discussion of the effects of different planting systems.