Answer: Arborvitaes tend to lose the inner leaves so to keep them thick and dense you should shear a few inches off them every spring. This forces new growth within the center of the plant. Another common problem with arborvitares are spider mites. These pests especially like dry places and the centers of arborvitae shrubs are perfect for them. You can discourage these pests by periodically hosing off the interiors of your shrubs to knock off the dust and dead foliage. Do this every 3-4 weeks during the spring and summer and you'll send the spider mites packing. Best wishes with your arborvitaes.
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