Alex needs to cut off a lower limb of a tree because it is in the way of people walking down the sidewalk. Trees in the woods loose their lower limbs when they are shaded out by the entire forest canopy. Trees are well adapted to losing their lower limbs. Trees planted in cities often require their lower limbs to be removed to make way for foot or vehicular traffic. But it is important to prune them a limb slowly, cutting off only a few limbs in a year and starting only after the tree has become established.
Lower limbs control root growth early in the tree's life.
Pruning correctly can be done anytime of the year. But if you can, avoid pruning your tree which of the following times. This will give it the best conditions for recovery. The canopy of leaves. Adding peat moss to the planting hole when planting a new tree will make it grow faster and give it a better chance at survival.