A Thuja occidentalis or Arborvitae is a tree from the Cypress family that has a natural pyramidal shape. It is usually planted as a specimen plant or to form a dense screen. The Thuja Arborvitae is adaptable to all areas of the United States. It grows to an eventual height of 25 to 40 feet and spread of 10 to 15 feet. The trees grow slowly for the first 10 years or so, then begin to grow rapidly and fill out. Many people are surprised at the sudden rapid growth and realize the trees were planted too close to a home's foundation or other part of the garden. In this case, pruning is necessary. For best results, prune every year, gradually reducing the tree's size, rather than attempting one drastic pruning.
Prune your Thuja Arborvitae in late winter or early spring before new growth begins to appear. New growth is lighter green than the rest of the foliage. Cut off the top off the Thuja Arborvitae at the desired height with electric or hand-held hedge shears. Make the cut evenly and cleanly across the top.
Begin on one side and cut at an angle from the top cut to the bottom of the plant tapering out as you cut down alongside the plant so the plant will retain the natural pyramid shape. Move around the plant, working from the top down on each side taking as little as 1 to 2 inches off at a time until you have regained the pyramidal shape. It is easy to make a mistake and take off too much on one side, so step back often and look at how the process is going before continuing.
Prune areas that need touching up to maintain the pyramidal shape after the foliage regrows later in the season. The loss of foliage and exposed bare limbs may be unsettling, but unlike many evergreens, a Thuja Arborvitatae will regrow foliage over the season.
Water the plant so it does not become stressed while recovering. Thuja Arborvitae trees appreciate deep moist, but not wet, soil.