Pruning simon's poplar helps it to grow more vigorously by directing energy to fewer branches, leading to stronger growth. It also maintains the tree's desired shape, enhancing its appearance and structural integrity.

Pruning or trimming simon's poplar during late winter or early spring is considered optimal because this timing aligns with the dormancy period of the plant and precedes the vigorous growth that typically occurs in spring. Pruning in late winter minimizes sap loss, which can be more substantial if pruning is done after spring growth has begun. Additionally, removing branches or limbs in late winter reduces the risk of disease transmission, as many pathogens are less active during cold weather. By trimming before the onset of new growth in early spring, wounds heal faster, and the plant can direct its energy into producing new, healthy growth, rather than repairing older, possibly damaged or diseased tissue. Moreover, without leaves, the structure of simon's poplar is more visible, allowing for more precise cuts and a clearer assessment of which branches should be removed for optimal plant health and shape.