Background Xylogenesis is synchronous among trees in regions with a distinct growing season, leading to a forest wide time lag between growth and carbon uptake. In contrast, little is known about interspecifc or even intraspecifc variability of xylogenesis in tropical forests. Yet an understanding of xylogenesis patterns is key to successfully com bine bottom-up (e.g., from permanent forest inventory plots) and top-down (e.g., from eddy covariance fux towers) carbon fux estimates. Methods Here, we monitor xylogenesis development of 18 trees belonging to 6 abundant species during 8 weeks at the onset of the rainy season from March to April 2022 in a semideciduous rainforest in the Yangambi reserve (cen tral Democratic Republic of the Congo). For each tree, the weekly cambial state (dormant or active) was determined by epifuorescence microscopy. Results We fnd interspecifc variability in the cambial phenology, with two species showing predominant cam bial dormancy and two species showing predominant cambial activity during the monitoring period. We also fnd intraspecifc variability in two species where individuals either display cambial dormancy or cambial activity. All trees kept>60% of their leaves throughout the dry season and the monitoring period, suggesting a weak relationship between the phenology of the cambial and foliar. Our results suggest that individual trees in Yangambi asynchro nously activate their cambial growth throughout the year, regardless of leaf phenology or seasonal rainfall. Conclusion These results are consistent with global analysis of gross primary productivity estimates from eddy covar iance fux towers, showing that tropical biomes lack a synchronous dormant period. However, a longer-term monitor ing experiment, including more species, is necessary to confrm this for the Congo Basin. As Yangambi is equipped with facilities for microscopic wood analysis, a network of inventory plots and a fux tower, further research in this site will reveal how xylogenesis patterns drive annual variability in carbon fuxes and how ground-based and top-down measurements can be combined for robust upscaling analysis of Congo basin carbon budgets. Keywords Cambial phenology, Tropical forest, Yangambi, Carbon storage, Congo Basin