On evergreen trees, avoid pruning the central leader (trunk). This results in the development of multiple leaders that are prone to wind and snow damage. If the central leader is killed back, select one branch to become the new leader and remove potentially competing leaders or you can put a splint on the new leader to hold it in position.
Never allow co-dominant trunks (trunks of similar size) to develop. If multiple trunks begin to develop, select one and remove others.
Size Control: In some ways, this is the weakest reason for pruning. If we plant the right tree in the right place, tree size should not be an issue. Almost all gardeners, however, have found themselves in the position where a tree grows faster than anticipated into other plants or buildings, and the need to keep that conifer in check arises.
Health: Removing dead, diseased, or damaged branches should be done anytime a problem pops up and can be safely corrected.
With few exceptions, conifers will not re-sprout if cut all the way back to the base, unlike many deciduous trees and shrubs.
Pruning method for cedars and junipers
Unlike some conifers, these trees will not form new buds on old wood. So if you cut back to the brown, aged stems, it won’t grow back. Pruning for size control, therefore, can only be done on new growth (where the stems are still green and pliable). Snip branch tips back where the cut will be covered by other foliage.
Pruning method for fir and spruce
To control height, prune the leader while the trees are dormant. These conifers form buds along their stems, so make a cut half an inch or so above a bud. The topmost bud will become the new leader. This cut will also stimulate outward growth of the buds below. Lightly trimming back the outermost branch tips during dormancy will also encourage fullness when the tree pushes new growth in spring.
Pines generally need little to no pruning.
On young plants, if a more compact new growth is desired, “pinching” may be helpful. Using the fingers, snap off one-third of the new growing tips while in the “candle” stage (in the spring when young needles are in a tight cluster). Avoid using pruners or a knife, as they will cut the remaining needles, giving a brown tip appearance..
With a mugo pine, cut it back to an even round shape. When the ‘candles’ bush out you will have a pleasing, feathery look.
Download the attached pdf document that demonstrates pruning conifers