The Rocky Mountain Juniper, like many varieties of the evergreen commonly known as cedar, grows to a mature height of about 30 to 60 feet. Because the natural growth habit is tall and symmetrical, very little pruning should be necessary. Trimming insect-damaged limbs, removing storm-damaged branches and cutting out fungal growths could be necessary.
If the juniper's lowest branches interfere with mowing or other property uses, prune the lower limbs of mature trees just before the junction with the trunk. Undercut a third of the diameter with a pruning saw and then complete the cut from above to limit splintering. Many low branches die back naturally--clip out dead or dying limbs with pruning shears or loppers. Major limbs drooping to inconvenient levels could be lightened by selectively thinning smaller branches. Use limb loppers or shears to remove a third of the side branches at the junction with the main limb. Heavy pruning could kill the branch.
Summer infestations of bagworm--a caterpillar that constructs a portable shell of juniper needles--should be controlled by spraying rather than pruning. The unsightly empty cocoons of the dead larvae remain on the tree and accentuate the missing foliage. Trimming out the cocoons with clippers can be done on small trees but involves clipping off twigs that would otherwise recover. Leaving the tree alone is the healthiest solution to the damage.
Use a pruning hook--also called a pole saw--to cut out storm-damaged upper branches. Many pole saws combine a pruning saw with a cord-operated limb lopper and have a reach of 20 feet. Pole saws also help when upper branches crowd buildings and over-grow rooftops.
In early spring, inspect the juniper for warty brown tumorous growths near the tips of branches. Cedar-apple galls indicate infection by fungus in the previous season. Removing the galls before they sprout orange tentacles and spread spores on the wind disrupts the disease cycle. Use a pruning hook to clip out any beyond easy reach.
Remove all clippings from the area after trimming. A rake pulls most lodged clippings out of branches without damaging the tree. Dead clippings soon turn brown and increase the fire danger by placing tinder in the vulnerable upper limbs of the juniper. Haul clippings away and dispose of them properly by chipping into mulch or burning in a safe location.