Evergreen trees, which retain their needles or leaves throughout the year, are often perceived as low-maintenance plants that rarely need attention. While their distinct growth patterns mean they require less frequent cuts than deciduous counterparts, evergreens can and should be trimmed to maintain their health, density, and structure. Understanding the specific needs of these year-round plants is paramount, as improper cuts or poor timing can cause damage that may never fully recover.
The Fundamental Difference: Trimming vs. Pruning
The terms trimming and pruning are frequently used interchangeably, but they describe two distinct actions with different goals. Pruning is a health-focused practice that involves making strategic, selective cuts to remove dead, diseased, or damaged branches. This process is essential for structural integrity, improving air circulation, and allowing light to penetrate the interior, which reduces the risk of pest and disease infestation. Pruning is typically performed with hand pruners or loppers. Trimming, in contrast, is primarily an aesthetic maintenance task focused on shaping the plant and controlling its size. Trimming is often done on hedges, shrubs, or formal plantings to give them a uniform, manicured appearance. While evergreens often need pruning to remove damaged wood, they require trimming only when a formal shape or size control is desired.
Timing is Everything: When to Cut Evergreens
The timing of any cut has a direct impact on an evergreen’s ability to heal and produce new growth due to its internal dormancy cycles. The optimal period for major structural pruning is late winter or very early spring, just before the first flush of new growth begins. At this time, the tree is still dormant, minimizing the stress of the cut and allowing the plant to use its stored energy for rapid wound closure once the growing season starts. Pruning during dormancy also permits clear visibility of the tree’s framework, making it easier to identify and remove structurally weak branches. A secondary window for light trimming and shaping occurs in mid-summer, typically after the initial spring growth has fully hardened. This timing allows for maintenance cuts without stimulating excessive new growth that is vulnerable to winter damage. It is inadvisable to perform any significant cuts in late summer or fall, as the subsequent flush of growth will not have sufficient time to harden off before freezing temperatures arrive.
Techniques Based on Evergreen Type
Evergreens must be categorized into two major groups based on their growth habit, as the cutting technique varies significantly between them.
Whorled Branching Species
The first group, which includes pines, spruces, and firs, exhibits a whorled branching pattern where new growth emerges from terminal buds. These species generally do not tolerate heavy cuts and must be pruned selectively to a side branch or bud. Pines require a specific technique known as “candle cutting” to control their size and increase density. This involves pinching or cutting the soft, upright new growth, called a candle, in half before the needles fully emerge and harden. Removing approximately one-half to two-thirds of the candle slows growth and redirects energy to the lateral buds, resulting in a bushier appearance. Spruces and firs are best reduced by cutting back to a lateral branch or bud to maintain their natural shape.
Random Branching Species
The second group, including yews, arborvitae, and junipers, features a random branching pattern with many small, latent buds. These species are far more tolerant of shearing and can be shaped into formal hedges. For size reduction, a selective cut should be made back to a healthy side branch that is growing in the desired direction, a technique known as thinning. Yews are a notable exception, as they have the ability to generate new growth from older, leafless wood, which allows for more aggressive rejuvenation cuts.
Critical Mistakes to Avoid
The most severe and common error when cutting evergreens is making a cut into the “old wood,” especially in pines, spruces, firs, junipers, and arborvitae. Unlike many deciduous trees, these conifers cannot regenerate new growth from stems that have lost their needles or scale-like leaves, creating a permanent, barren spot. This dense, leafless interior is often referred to as the “dead zone,” and any attempt to prune past the green, active foliage will result in a brown stub that will not recover. Another irreversible mistake is “topping,” which involves removing the central, dominant leader at the top of the tree. Topping destroys the tree’s natural conical shape, compromises its structural integrity, and often leads to the growth of multiple, weak, upright shoots. This practice creates a structural hazard and stresses the tree, making it more susceptible to disease and insect infestation. Finally, removing too much foliage in a single season can severely weaken the plant by reducing its photosynthetic capacity. A general rule is to never remove more than 25 to 30 percent of the total foliage mass in one year.