Beginning of the full bloom of the apple

Background information

The time of flowering is strongly dependent on average temperatures in late winter and spring, and is also influenced by night temperatures. Apple blossom is particularly sensitive to late frosts. Although late frosts are also becoming less frequent as a result of climate change, the reduction is less pronounced, meaning that early apple blossom is still at greater risk of frost damage.

Description of the graph and the results

The graph shows the calendar day of the Golden Delicious apple variety‘s full flowering in each year from 1975 to 2025. Despite the high variability in individual years, it is clear that flowering has occurred earlier and earlier over the last 51 years. In 2025 this was on 08 April. On a linear average, apple blossom starts about 13 days earlier than in 1975.

Method

The graph is based on the phenological studies carried out by the Laimburg Research Centre on Golden Delicious, adapted for apples using the international BBCH code lists (Fleckinger development stages). BBCH is the official abbreviation for Biologische Bundesanstalt für Land- und Forstwirtschaft, Bundessortenamt und CHemische Industrie. It provides information on the morphological development stage of a plant. The observation took place on the sandy loam soil type with 2.1 to 2.7% organic matter and a pH value of 7.1 to 7.4 at the Laimburg site (220 meters above sea level). Cultivation follows the guidelines of integrated cultivation.

Sectors affected

• Agriculture

• Biodiversity

Related indicators

Contact

Eurac Research: Georg Niedrist, Institute for Alpine Environment

Data provided by the Research Center Laimburg, Walter Guerra