Answer: The older, inner leaves of arborvitae (globe spruce) naturally turn brown and drop in the autumn (similar to the loss of leaves on deciduous trees). This shouldn't cause alarm, and does not indicate disease. If the tips of the branches are turning brown, look for infestations of spider mites (they leave tiny webbing between the junctions of the leaves and stems), or consider cultural problems such as over- or under-watering. Sometimes the leaf tips will turn brown because they've been exposed to sudden temperature changes. Since your globe spruce has only recently been planted, i may be going through an adjustment period. Give it about an inch of water every week, and wait until spring to reassess the situation. By then it should be better established in its new home and you can prune off the brown plant parts to encourage healthy new green growth.
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