The primary reasons to prune conifers include shaping, removing diseased or damaged limbs, and removing limbs that obstruct a view or interfere with power lines, roadways and structures.
When and how to prune depends on the growth habit of the conifer. Conifers typically fall into two broad categories: (1) those with branches that radiate out from the trunk in whorls and (2) those with branches that sprout in a random manner.
Whorl-type conifers include fir (Abies), spruce (Picea) and most pines (Pinus). Whorl-type conifers have only one flush of growth in the spring and should be pruned in early spring before soft new growth becomes mature.
New growth on whorl-type conifers is often called “candles.” Buds appear at the tips, along the sides and at the base of the candle. Removing or pinching back the candles before their needles lengthen and harden promotes dense branching and shorter limbs.
Because whorl-type conifers have few dormant buds outside the areas of new growth, avoid cutting into the older wood — unless removing the entire branch — because there will be no regrowth and the branch will remain a bare stick.
Random-branching conifers include cedar (Cedrus), cypress (Cupressa), juniper (Juniperus), arborvitae (Thuja), yew (Taxus) and hemlock (Tsuga). Random-branching conifers grow in spurts throughout the season and can be pruned in early spring before growth starts, in mid- to late-summer, or in winter when the plant is dormant.
To shape a conifer, begin with a cluster near the top of the tree. Trim the leader — the dominant upright branch — several inches. The leader should be the longest stem of the cluster. Trim remaining stems proportionately shorter than the leader. Repeat this process around and down the tree, maintaining a proportionate and natural shape.
When removing a branch in tree pruning, always try to remove it without cutting into the branch collar (the swollen area of trunk tissue that forms where the branch meets the trunk). On branches small enough to be removed with a hand pruner, position the hand clipper just outside of the branch collar and cut.
For larger branches, use the following three-step process to avoid tearing the bark beneath the limb that is being removed and/or damaging the collar.
Choose a site 12 inches from the trunk and saw halfway through the underside of the branch.
Reposition the saw to the topside of the branch 1 inch further away from the trunk than the underside cut. Begin sawing toward the underside cut; the branch will collapse off the tree.
Move to the trunk of the tree and position the saw just beyond the branch collar. Cut down and outward through the branch at a 45- to 60-degree angle.
Tools needed for pruning include a sharp hand pruner and hand saw. To avoid spreading disease while pruning, disinfect the pruner or saw by spraying with 70 percent alcohol before moving to a new branch or tree. If pruning requires using a ladder, make sure the ladder has a solid and level footing.
Judy English is a WSU-certified Clallam County Master Gardener.