J. For. Sci., X:X | DOI: 10.17221/6/2026-JFS

Soil temperature and weather factors as key drivers of flowering phenology and nectar production in black locust (Robinia pseudoacacia L.) in HungaryOriginal Paper

Alexandra Porcsin¹, Tamás Ábri ORCID...², Helga Déri ORCID...³, Edit Zajácz ORCID...³, Bence Bolla ORCID...⁴, Katalin Szakálosné Mátyás¹, Károly Rédei⁵, Zsolt Keserű ORCID...²

¹ Faculty of Forestry, Institute of Natural Resources and Forest Management, University of Sopron, Sopron, Hungary

² Department of Plantation Forestry, Forest Research Institute, University of Sopron, Püspökladány, Hungary

³ Department of Apiculture and Bee Biology, Institute for Farm Animal Gene Conservation, Gödöllő, Hungary

⁴ Department of Forest Ecology, Forest Research Institute, University of Sopron, Budapest, Hungary

⁵ Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Debrecen, Hungary

The black locust (Robinia pseudoacacia L.) is the second most planted tree species worldwide, and the most common in Hungary. Phenotypic traits, particularly flowering patterns, are well-established indicators of the species' response to climate change. This study examined four forest subcompartments across three Hungarian regions: Northern-Central, Eastern and Southern-Central. The aim was to identify climatic factors correlating with the onset and duration of the flowering period. Additionally, the relationships between these factors and nectar weight and sugar concentration were defined. Results indicate a strong negative correlation between precipitation levels and flowering time: lower accumulated and average precipitation during the spring months of the preceding year was associated with a delayed flowering period in the following year (r = –0.922, r = –0.918, P = 0.05). However, when examining the 14-day period (r = 0.829) before blooming or examining from 1 January (r = 0.929, r = 0.890), the results indicate that other environmental factors may play a more dominant role. Furthermore, the number of chill and heat days was found to affect the starting date (R² = 0.819, R² = 0.765).

Keywords: apiculture; cultivars; flowering date; phenological plasticity; weather factors

Received: January 19, 2026; Revised: March 26, 2026; Accepted: March 30, 2026; Prepublished online: April 17, 2026