Apricot flowering time prediction using growing degree hours

Apricot fruit growers try to prevent late spring frosts damages of flowers by various technical measures. But with regard to longer-term planning they need to know at least approximately the flowering date in the given year. The method of apricot (Prunus armeniaca L.) flowering date prediction using temperature models is elaborated in this work. Phenological phases of beginning of apricot flowering at locality of Velké Bílovice (Břeclav district, Czech Republic) were recorded in years 1998-2018. Calculations of growing degree days (GDD) and growing degree hours (GDH) were performed. Calculation of GDH expressed as sums of effective temperatures (SET) with base temperature +5°C corresponded to flowering time as the most accurately and can be used to predict the apricot flowering day. Based on the performed calculations GDH sum of 2600°C expressed as SET+5°C from the January 1^st can be considered suitable for prediction the beginning of flowering of early to medium early flowering apricot cultivars.