Fragrant Western red cedar foliage remains green year-round.

How to Maintain Western Cedar

by Jessica Westover

The western red cedar (Thujia plicata), also known as western cedar, western arborvitae or giant arborvitae, hails from the northwestern United States. This evergreen reaches heights of 50 to 200 feet and produces thick, scale-like foliage on trunks with auburn, peeling bark. Hardy in U.S. Department of Agriculture plant hardiness zones 5 through 7, the western red cedar thrives in the cool, moist climates characteristic of its native regions. It prefers full to partial sunlight and moist, nutrient rich, fast-draining, alkaline to acidic soils. A western red cedar requires basic maintenance to keep it healthy and beautiful.

Pull weeds from the ground surrounding and underneath the western red cedar's canopy. Spread a 2 to-3-inch deep layer of mulch over the ground with a rake. Keep the mulch 4 inches away from the tree's trunk to prevent its bark from rotting. Replenish or replace the mulch each spring.

Water the tree when the top 2 inches of soil becomes dry or when less than 1 inch of rain falls during a period of seven days. Apply 1 to 2 inches of water from a garden hose directly to the ground. Water in a circle around the tree, beginning at the trunk and extending outward in a radius equal to twice the canopy's radius.

Prune the western cedar in late winter or early spring, just before it breaks out of dormancy. While you are pruning, take time to smell the fragrance emitted from broken twigs and branches that many people use for indoor wreathes and swags. Remove any dead branches, cutting each one back to 1/4 inch above the branch bark collar, or swollen ring surrounding its base. Use pruning shears to cut branches with diameters of 1/4 inch or less, loppers for diameters of 1 1/2 inches or less and a pruning saw for diameters greater than 1 1/2 inches. Cut back any diseased or broken branches to healthy wood, making the cut 1/4 inch above a lateral branch or the branch bark collar. Trim back any vigorously growing or overly long branches to shape the tree. Do not trim any branches back into old leafless wood because it contains no living leaf buds.

Fertilize the western red cedar with a 10-10-10 nitrogen, phosphorous, potassium slow-release granular fertilizer in the spring, just prior to the start of new active growth. Apply the fertilizer at a rate of 1 tablespoon per square foot of soil. Broadcast the granules in a 12-inch wide band beginning just underneath the canopy's perimeter and extending outward. Rake the fertilizer into the top 3 inches of soil. Water the area thoroughly.

Items you will need

  • Mulch
  • Rake
  • Garden hose
  • 10-10-10 (n-p-k) slow-release granular fertilizer
  • Pruning shears
  • Loppers
  • Pruning saw


  • Soak the blades of your pruning tools in a solution of one part 70 percent isopropyl alcohol and one part water for five minutes to sterilize them before and after pruning the tree. Sterilize the tools after making a cut into diseased wood to prevent spreading the disease.


  • Wear gloves when spreading mulch, fertilizer or pruning to protect your hands from injury and prevent direct contact with diseases.

Photo Credits

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