Reconstructing annual leaf production in evergreen trees is still challenging, even though leaf production is one of the determinants of carbon sink capacity of forests. The purposes were to reconstruct the yearly variations in leaf production from annual shoot lengths and to clarify if the climatic drivers are the same between reconstructed leaf production and stem radial increment, which has been used as an indicator of annual productivity. Ten mature Picea mariana trees were harvested from an open pure stand in North of Canada. A robust linear relationship was obtained between annual shoot length and leaf dry mass on it. Annual shoot lengths on primary branches were measured for over twenty years. The yearly variations in these lengths were synchronized not only within, but also among individual trees, indicating that the main drivers of these variations acted at the stand level. The climatic drivers of reconstructed leaf production were the late summer temperature in the current year and early summer temperature in the previous year, while no significant variable was selected for stem radial increment. Thus, the response to global warming might be different between leaf production and stem radial increment and measuring each of them separately is therefore important.