Poplars grow quickly, adding 5 to 10 feet annually up to a mature height of 50 to 100 feet. Trim them in late winter or early spring before new growth starts. You need pruning shears, a pruning saw, bleach and a ladder.
Prepare your tools
Prepare one part bleach to 10 parts water in a bucket, and soak your tools to disinfect them. Periodically re-disinfect the shears and saw during the pruning process.
Shape young trees
Trim the young tree during the early years of growth, removing side branches to ensure a columnar shape. There should be one vertical leader with side branches coming out of it. Shaping the tree is much easier when it is short and you can reach the top.
Trim the tree for health and appearance
Dead branches do not sway in the wind and sometimes have wounds or discoloration. Branches that cross other branches will cause later damage. Downward-facing branches do not allow sunlight to nourish the tree. Use a pruning saw to cut these off at the base near the branch collar. Low-growing branches and suckers growing from the trunk can also be trimmed away. When you are finished, clean up any leaves or remains from under the tree to prevent fungus growth and disease.