No need to worry! Your arborvitae (Thuja) plants are probably just experiencing their annual needle replacement.

Even an evergreen plant replaces its foliage. When you see brown needles on the inner part of arborvitae in fall, it may not be a problem: it is normal to see brown leaves in older growth areas, as that foliage is just aging and will eventually be shed, sometimes dramatically. The brown needles may remain on the tree for months before coming off in branchlets.

If you are experiencing browning on your arborvitae in another season, please refer to our Guide to Arborvitae for help determining what could be happening to your plant.

Courtesy of NYBG Plant Information Service