The European larch Larix decidua is one of the most important tree species in Polish forestry. It is valued both for the economic quality of its wood and for its biocenotic importance. Against the background of climate change, research into phenological variability and reproductive capacity is becoming increasingly important. Such studies can provide information on the future adaptive potential of this species under changing environmental conditions. The aim of this study was to investigate and analyse the clonal variation of vegetative bud development and the intensity of flowering in the European larch in a seed orchard in Sękocin Stary. The research material consisted of 40 clones planted in 2017 on dwarf rootstocks and spaced 4×5 m apart over an area of 0.05 ha. The observations were carried out in spring 2025, between 21 March and 16 April, at intervals of 2−3 days using a five−point scale. Based on a visual assessment of the number of female and male flowers in the tree crowns, the intensity of flowering was evaluated according to the scale used. The collected data were subjected to detailed statistical analysis, including analysis of variance (ANOVA), Tukey test, linear regression and Spearman rank correlation analysis. The results of flowering intensity showed a greater variability in the production of female flowers compared to male flowers. Clone 7696 was characterised by the highest flower production, while clones 7017, 7004 and 704 produced few or no female flowers. In contrast, the male flowers showed a high level of flowering and statistically significant differences were found in the ANOVA analysis. However, these differences were not confirmed by the post−hoc test, which could indicate a lower importance of this parameter. The results show a strong influence of genetic factors on the phenology and reproduction of European larch. In tree breeding, the most valuable clones are those that show an early and stable phenological development in combination with a high productivity of both male and female flowers. These results can contribute to the refinement of selection methods and support strategies for adapting to a changing climate.

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