Culture Notes
Transplanting is moderately easy if plants are root-pruned and either balled and burlapped or potted. White-Cedar likes high humidity and tolerates wet soils and some drought, but not salt exposure of any kind. The foliage turns brownish in winter, especially on cultivars with colored foliage and on exposed sites open to the wind. Many of the natural stands in the United States have been cut. Some remain in isolated areas along rivers throughout the East.
Planting and establishing shrubs
The most common cause of young plant failure is planting too deep. Plant the root ball no deeper than it was in the nursery. In most instances, the root flare zone (point where the top-most root in the root ball originates from the trunk) should be located just above the landscape soil surface. Sometimes plants come from the nursery with soil over the root flare. If there is soil over this area, scrape it off. The planting hole should be at least twice the width of the root ball, preferably wider. In all but exceptional circumstances where the soil is very poor, there is no need to incorporate anything into the backfill soil except the loosened soil that came out of the planting hole. Never place ANY soil over the root ball. If a row or grouping of plants is to be installed, excavating or loosening the soil in the entire bed and incorporating organic matter enhances root growth and establishment rate.
Weed suppression during establishment is essential. Apply a 3-inch thick layer of mulch around the plant to help control weed growth. Keep it at least 10 inches from the trunk. If you apply it over the root ball, apply only a one or two inch layer.  This allows rainwater and air to easily enter the root ball and keeps the trunk dry. Placing mulch against the trunk or applying too thick a layer above the root ball can kill the plant by oxygen starvation, death of bark, stem and root diseases, prevention of hardening off for winter, vole and other rodent damage to the trunk, keeping soil too wet, or repelling water. Regular irrigation through the first growing season after planting encourages rapid root growth, which is essential for quick plant establishment.
Pests, Diseases and Damaging Agents
Pests: Arborvitae leaf miner mines out the leaf tips, causing them to turn brown. Scales of several types infest the stems and foliage. Mites cause yellowing and speckling of the foliage. Bagworms can devour large quantities of foliage very quickly. Deer enjoy browsing the plant and can cause significant damage or death of the plant in some instances.
Diseases: Leaf blight causes brown spots on the leaves in late spring.Â