Cedar trees and shrubs are evergreen plants from the genus Cedrus, which consists of Himalayan cedar (Cedrus deodara), which is hardy to U.S. Department of Agriculture plant hardiness zones 7 and 8, Atlantic cedar (Cedrus atlantica), hardy to zones 6 through 9, cedar of Lebanon (Cedrus libani), hardy to zones 6 and 7, and various cultivars of these species. Cedars make dense, low-maintenance hedges and can add color to your landscape year-round if given the proper care.
Cedars thrive in sunny, open sites. When planting as hedges, do not place cedars near walkways or driveways where salt may be used over the winter. Salt can seriously damage the foliage. Keep the shrubs at least 3 to 4 feet away from these areas and from property edges, and choose a sunny to partly shaded location. Avoid sites where your hedge is in full shade. Cedars won’t grow properly without sunlight. Space each plant 12 to 18 inches part to allow for good air circulation, which prevents pest and disease problems. Do not plant cedar hedges on sloped areas, because moisture will run down the slope and away from your hedge.
Cedars do best in moist, well-drained, nutrient-rich, acidic to neutral soils. To ensure dense, green growth cedar hedges need nitrogen. Fertilize cedar hedges with a water-soluble evergreen fertilizer that is high in nitrogen, such as 30-10-10, in May, June and July. A slow-release nitrogen and phosphorus fertilizer in late fall gives shrubs an extra boost for producing new growth in the spring. Broadcast the fertilizer over the soil, keeping it away from the trunk, and water it in thoroughly.
Cedars like moisture, but they don’t require frequent watering. In hot, dry weather, water deeply to prevent browning and drought stress. Otherwise your hedge only needs water when the soil feels dry to the touch. A layer of mulch at the base of your cedar hedges but slightly away from the trunk helps retain soil moisture and prolongs the time between watering.
The key to an attractive and healthy cedar hedge is proper pruning. Cedar hedges require topping to control height, and light to moderate pruning of the sides for shape. Never remove more than 1/4 of the tree’s height at one pruning, and shape your hedge so that the top of each plant is narrower than the bottom. This allows sunlight to reach all parts of the plant, which ensures a green hedge from top to bottom. Cedar hedges can be pruned at any time, but the ideal time to prune is usually July or August, because the first flush of spring growth has slowed and new buds produced after pruning have time to harden off before the first frost. Spring pruning may remove terminal buds, which slows the plant’s growth, and fall pruning may cause the hedge to produce a late flush to recover lost buds, and these new buds may not have time to harden off before frost arrives.
Cedar hedges are vulnerable to damage caused by aphids, scales and bark beetles. Aphids and scales feed on plant sap and secrete honeydew, which promotes sooty mold growth, causing distortion and discoloration of foliage. Rinsing foliage with clean water may reduce aphid populations and removes honeydew. Treat severely infested plants with foliar applications of insecticidal soaps or oils, or insecticides containing malathion, permethrin or acephate. Bark beetles (Phloeosinus spp.) are more difficult to control because once damage is visible, insecticides are usually ineffective. These small, dark red, brown, or black insects leave a buckshot pattern of holes on the bark and cause dead tips on twigs. Proper watering and pruning to prevent overcrowding of plant parts can prevent bark beetle problems. Existing infestations may be controlled by pruning damaged parts or by removing and replacing heavily infested plants.