Treeline ecotones are exposed to pronounced differences in irradiation and nutrient availability in complex mountain relief. We compared growth phenology and growth rate of Picea abies on north- and south-facing slopes at sites differing in nutrient availability at the lower part of the treeline ecotone. Our results suggest that temperature alone governs growth phenology, but nutrient availability modulates the growth rate in the peak season when temperature no longer limits cambial activity.