Columnar evergreens fit into landscape sites when other trees just won't do. They add a stately air without overwhelming gardens and break up the horizontal lines of roofs and fences. Unlike some evergreens, these cultivars stay trim, but they do require extra consideration; they are not suitable for every situation.
Columnar evergreens with a compact footprint fit neatly between houses or along property lines to screen your home from the neighbor's view. Landscapers incorporate them for height in small-scale designs, adding winter interest when other trees are dormant. Plant them in a row for a highly formal effect or as bold vertical accents in a modern landscape. To a lesser extent, narrow trees are small-scale windbreaks, reducing noise and dust from nearby roads.
Because columnar evergreens often grow up rather than out, their branches have narrow-angled crotches that are not as strong as wider-angled branches. If you live in an area that receives heavy snows, consider wrapping the evergreen with a fabric binding designed to support these trees. Water the evergreen well before winter sets in to prevent damage from drying winds. When pruning, don't prune deeply; most evergreens don't regrow foliage from bare wood.
Consider the mature diameter of the evergreen trees before you plant, and plan accordingly. Give each tree enough space to provide adequate air circulation; crowded trees encourage disease and pests. Also, even though the trees are narrow, their root systems are not. Crowded roots stunt the tree's growth, limit access to nutrients and may damage sidewalks or other structures. If you plant columnar trees for privacy, stagger them or plant the evergreens in a triangular cluster. The trees still provide a dense screen if they are all in the same line of sight, but at different distances.
Although you may be tempted to plant a neat row of the same columnar evergreen down the side of the fence, keep in mind that if just one of these trees fails or succumbs to disease, your effect is ruined. Landscapes that depend on uniformity rarely succeed without dedicated, constant maintenance. Since many evergreens have moderate or slow growth rates, it takes many years to regain the formal effect. Instead, consider a variety of columnar evergreens. Not only is this planting style more natural, it is also creates a welcoming landscape.
Look for evergreen cultivars with variations of "fastigate" or "columnar" in the botanical name. This often indicates a narrow, columnar form. Italian cypress (Cupressus sempervirens), suitable for U.S.Department of Agriculture plant hardiness zones 7 through 10, grows from 20 to 30 feet tall but just 3 to 5 feet wide. "Skyrocket" Rocky Mountain juniper (Juniperous scopulorum "Skyrocket"), hardy in USDA zones 4 through 9, is drought-resistant and similar in size to the Italian cypress. Fastigate Eastern white pine (Pinus strobus "Fastigiata"), hardy in USDA zones 3 through 8, grows 30 to 40 feet tall with a 7- to 10-foot spread.