Answer: Browning foliage is usually a water stress issue but might also be sunscald, depending upon where the brownin is occuring. Newly planted trees and shrubs take a while to adjust to their growing sites and new foliage is especially tender and sensitive. Poorly draining soils can cause as much stress as droughty conditions so you may want to poke a stick down into the soil to see how moist it remains after watering. Moist soil will be easy to probe; dry soils will give some resistance. Aside from watering issues or sunscald, there's really no reason for new arborvitaes to develop brown foliage. Hope this information helps you determine the cause. Best wishes with your arborvitaes.
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