How to Protect Arborvitae

Give your tree the well-drained soil it requires to stay healthy by adding up to 6 inches of compost to the planting hole. Arborvitaes weaken and even die when planted in clay or other water-holding soil. Provide the tree with a long drink of 5 to 10 gallons of water weekly during hot or dry weather but no more; overwatering is as much a problem for the trees as underwatering. Good cultural practices protect an arborvitae from pests and diseases that attack stressed trees such as pestalotiopsis, a needle blight fungus.

Position the trees with sufficient room to develop based on research about your arborvitae's mature size. Too-close spacing is a frequent problem with arborvitaes, a popular choice for "emergency" privacy hedges. Space hedge trees at least 4 feet apart; increase that to 6 feet for larger varieties. Trees of the genus Thuja feel a squeeze in a few seasons when overcrowded in a hedge or close grouping. Without sufficient air and light, arborvitae get stressed and are less cold hardy.

Water once just before the first winter frost but do not apply anti-desiccants. The tree's needles often do not harden off sufficiently and, after anti-desiccant application, the moisture remaining in the plant cells freezes and bursts. Avoid fertilizing young arborvitaes if you live in a climate with harsh winters; fertilized trees produce soft, fragile growth that cold-burns in winter.

Wrap pieces of burlap around young arborvitaes, attaching the material securely with rope or sturdy twine in later fall before the first snow. Keep the wrapping snug but not tight enough to damage the branches. Alternatively, wrap the trees with three-strand jute twine. Start wrapping at the bottom of the tree and working up. For multi-stemmed trees, attach the main stems together in several places; pull the stems together snugly but avoid deforming the tree or breaking branches. Remove winter protection in early spring to allow the tree branches to move freely. Generally winter protection is only required for the first three years after planting.

Spray Eastern arborvitae (Thuja occidentalis, USDA zones 2 though 7) with organic deer repellent early in winter to prevent unwanted pruning of your shrubs by hungry Bambis. Repeat the spray every month during winter or per label directions. Fencing also provides good deer protection.