Pruning an Evergreen Tree
Pruning an evergreen tree or shrub is often necessary in order to limit the size of the plant, correct irregular growth, or maintain a desired form (such as a hedge). Normally, the natural form of most evergreens is the most desirable. Generally, there are two main types of evergreens, and because of their different habits of growth, they must be pruned differently. One type of conifer may be referred to as ‘whorl-branching’ since the branches grow out from a main trunk, often in a whorled pattern. This type includes pine, spruce, and firs. The other type of evergreen branches in a random fashion, most often with no central trunk, Junipers, arborvitae, and yews fall into this category.
How Evergreens Grow
Evergreens make their new growth from buds that were formed the year before. These buds are usually brown and are often found on the terminal end of each branch. In addition to these large terminal buds are many more smaller side buds which usually do not grow. Pruning of the terminal bud will redirect the growth by stimulating the side buds to sprout and grow. Instead of growing up or out with a limited number of terminal buds, the sprouting side buds will create more branching. The plant will look denser and more compact.
Pruning Whorl-Type Branches
Pines are most effectively pruned by ‘pinching the candles’ of light-colored new growth during their short growing season, usually the month of June. Pruning the candles after June may result in dead stubs, since the new growth that was forced out after this pruning may not have had enough time to harden off before winter and may become cold-injured. You can prune up to one-half of the new growth, if necessary. The more you prune, the denser and more compact the pine will become. Dwarf mugho pines benefit greatly from such pruning every one to three years. Spruce and fir tend to grow in one or more flushes during the growing season. They are best pruned in the same manner as pine by pruning after the first flush of growth is about three-fourths of the expected length. The time for this is usually about early to mid-June.
Pruning Random-Branched Evergreens
Evergreens, such as juniper, arborvitae, and yew grow continuously during the growing season and can be pruned at almost any time before August. Pruning after August can cause any evergreen to become more susceptible to winter injury. Random-branched evergreens may be pruned by removing entire branches, pinching the new tip growth in the spring, or shearing. Any of these methods will help control the size of the plant. Creeping junipers usually only need to have their new growth ‘tip-pinched’ and dead branches removed. Shearing is usually recommended for hedges and formal topiary shapes only. Remember, the natural form usually looks best.