Green up in Biotechnical school Maribor, Slovenia - hazel tree

2025-06-09T18:41:22Z

Hello!
We have been monitoring the development of hazel for the third year in a row. We have been observing the same branch all three years. (Skoke: N 46.4859, E 15.6968, Elevation 263 m).
Hazel have been observed in year 2025 since February 6th. They completed the measurement on May 29th.
Green up measurement results from 2023 to 2025:
Leaf length 2025: Leaf 1 - 92, Leaf 2 - 87 mm, Leaf 3 - 93 mm, Leaf 4 - 104.
Leaf length 2024: Leaf 1 – 78, Leaf 2 – 82, Leaf 3 – 74, Leaf 4 – 72.
Leaf length 2023: Leaf 1 – lost, Leaf 2 – 82, Leaf 3 – 77, Leaf 4 – 62.

This year, the average temperature during the measurements was the lowest (8.9 °C), in 2024 it was 11.5 °C and in 2023 11.3 °C. There was a similar trend in precipitation. This year, 227.8 mm of precipitation fell during this period, in 2024 272.6 mm and by far the most in 2023, as much as 389.8 mm. Despite less precipitation and lower temperatures, the leaves developed the most this year. This year they are 17.5 mm longer than in 2024 and as much as 20.3 mm longer than in 2023. From these results, we can conclude that temperature does not have the most significant influence on the length of hazel leaves, as the amount of precipitation does not. However, it is certainly important that the rain fell very evenly and there were no dry periods in between.

Best wishes,
Simon Gračner with students