Spring shock syndrome (SSS) is a condition where flowering and leaf development in peach and nectarine trees is delayed and those leaves that do develop are often small and discoloured. Trees experiencing spring shock syndrome yield poorly. To learn more about the development of this syndrome, this thesis has examined the influence of root zone temperature (RZT) and genotype on the growth of peach rootstocks and the scions grafted onto them. Other factors that influence the quality of peach seedling rootstocks were also examined. Initial trials examined the influence of Okinawa (a low chill cultivar) and Golden Queen (a high chill cultivar)rootstocks on the expression of SSS. Studies found that multiple stems could originate from either multiple seeds within a single stone or from axils originating from the base of cotyledons. The incidence of both conditions was heavily influenced by variety, thus suggesting that an active selection program based on the elimination of these traits would be beneficial to the stone fruit nursery industry. / Doctor of Philosophy (PhD)