White cedar (Thuja occidentalis), a coniferous evergreen, grows to nearly 50 feet tall, and is commonly used as hedging or, sometimes, for shading in landscapes. White cedars are relatively low-maintenance trees, requiring only moderate pruning of healthy divisions for dimension control, and elimination of diseased divisions for plant health. Pruning in late winter or early spring works perfect for white cedars, permitting the trees time to recuperate before the growing season.
Examine your white cedar for diseased and broken limbs and branches. Place a piece of bright fluorescent tape on each to make locating them easier.
Eliminate large diseased and damaged limbs by first making an undercut halfway during the limb eight inches to 1 foot from the back, using a handsaw or pole saw. Subsequently try to find an overcut that meets the undercut in the middle. Use an orchard ladder when the pole saw doesn’t get to the limb.
Eliminate the stub of this damaged or fragile limb by first making an undercut just from the branch collar at a slight upward angle from the tree, then using the handsaw or pole saw. Make sure that the undercut meets with an overcut, continuing the slight upward angle. The angle helps protect the rain from the exposed wood.
Eliminate smaller diseased and broken branches using bypass pruning shears, again making a cut in the branch collar. Wipe the blades of their saws and shears with a lint-free cloth moistened with isopropyl alcohol after cutting diseased wood.
Locate all tangled or crossed branches and identify the weakest of this group. Signs of weak branches include drying, splitting and feeble branch collars. Eliminate the weakest crossed or tangled branches with the hand shears or pruning saw, depending on their thickness.
Trim back the division tips marginally to help handle tree size. You can only prune new growth, not brown, older stems, for size control over a white cedar, since new buds won’t grow on older wood.
Reduce the branches of their white cedar to make it narrower on top than on the underside, using hand shears, the pole saw or the handsaw. Opening up the tree using this procedure helps all of the branches receive sunlight. Make sure you leave a minumum of one green, hardy shoot on each trimmed branch.