The Effect of Four Controlled Winter Temperatures on the Flowering and Fruiting of the Apple

SummaryTwo-year-old potted trees of Cox’s Orange Pippin, Laxton’s Superb and Worcester Pearmain were grown in controlled environment chambers at Long Ashton during 1960 and 1961, and subjected to four types of winter temperatures : 1, a long, cold winter ; 2, a severe autumn and mild spring ; 3, a mild autumn and severe spring ; 4, a short, mild winter ; 5, natural winter.The order of bud break was treatment 2 followed by 4, then I and lastly 3. The time of bud break was more strongly influenced by the date of winter chilling than by its intensity, but the intensity influenced the temperature at which bud break became possible. On I-year-old wood the number of leafy rosettes developing increased with the length of the chilling period.Because of limitation of space and the consequent small number of trees used, no firm conclusions could be drawn, but flower bud production and rate of spur development from bud break to full bloom appeared to be favoured by a mild autumn. An early and severe autumn apparently increased flower bud abscission at green cluster, but no effect of treatments could be determined in the final yields of fruit.