The white cedar (Thuja occidentalis), also called the American arborvitae or Eastern white cedar, produces a pyramidal, conical growth habit that adds an air of formality to the landscape. The dense, green to yellowish-green, scalelike foliage stands out among evergreens and deciduous trees alike, making the white cedar useful as a focal point, screen, hedge or border. Hardy in U.S. Department of Agricultural plant hardiness zones 2 through 7, this woody evergreen thrives in nutrient rich, moist, fast draining soils, humid regions and full to partial sunlight.
1 Pull weeds and remove debris from the ground encircling the white cedar. Clear a circular area with at least a 2-foot radius. Spread a 2-inch deep layer of mulch over the cleared area with a rake. Keep the mulch 3 inches away from the cedar's trunk to prevent it from rotting.
2 Water the white cedar when the top 2 to 3 inches of soil becomes dry. Apply at least 2 inches of water from a garden hose to moisten the entire depth of the root zone. Do not water so frequently as to allow the soil to become soggy or develop standing water.
3 Fertilize the white cedar with a 10-10-10 nitrogen, phosphorous, potassium slow-release granular fertilizer once per year in the early spring, just prior to the tree breaking out of dormancy. Apply the fertilizer at a rate of 2 to 3 teaspoons per square foot of soil. Broadcast the granules in a 12-inch wide band around the tree, at least 6 inches away from the trunk. Use a rake to mix the fertilizer into the top 3 inches of mulch and soil. Water the area thoroughly.
4 Spray the foliage with a steady stream of water from a garden hose to wash off accumulated dirt, dust and debris that may attract insect pests. Wash the foliage during the morning hours to allow it time to dry before nightfall. Repeat this process every 2 to 4 weeks.
5 Prune the white cedar once per year in the early spring to remove any dead or broken branches. Make each cut 1/4 inch above the swollen ring, or branch bark collar, at the limb's base. Use a pair of pruning shears to cut branches with diameters less than 3/4 inch and loppers for diameters greater than 3/4 inch.
6 Winterize the white cedar tree in the late fall or early winter if the tree remains less than 6 feet in height and you live in a climate that receives heavy snow fall. Wind a piece of twine string around the white cedar's canopy, one-quarter of the way below its top. Tie the ends of the twine together in a knot, making the string loose enough to allow some movement, but tight enough to hold the branches together to prevent them from bending backward and breaking under the weight of snowfall. Wrap a piece of burlap loosely around the cedar's canopy, covering it completely but leaving the top open. Tie the burlap in place with string. Remove the burlap and string in the late winter or early spring once the snow begins to melt.