Relationship between temperature and flowering in almond

Abstract

Records of flowering in 12 almond cultivars over 7 years, together with temperature records from a standard climate station, were used to estimate the chilling requirement for dormancy break in flower buds and the heat sum requirements for floral development in each cultivar. Hourly temperatures were estimated from daily minimum and maximum temperatures. A continuous function relating hourly temperatures to rate of chilling was used to calculate daily chill unit accumulations. Requirements of 220-320 chill units were estimated and calculated heat sum requirements ranged from 5300 to 8900 growing-degree-hours above 4-5°C. These requirements were used to estimate the dates of 50% flowering for 1958-84.