Question
Hello,\

I have a bank of Pyramidalis, planted 24in apart. They are about 20 years old and 20 feet tall and have been very healthy. This year I have noticed that the interiors are thinning out and browning, as well as the tops are turning yellow/brown. We live in Seattle WA.

Can we save them?

Answer
Like all evergreens, arborvitaes will shed some of their inner, oldest growth each year. Evergreens do not hold their needles forever, they just hold them year-round for several years. How long an evergreen holds its foliage depends on the variety. Arborvitae tend to hold foliage 3-4 years. As the plant ages, each fall the oldest foliage will yellow, brown and shed. That is natural. This internal browing of the needles is natural and nothing to worry about.

One cause of browning on a Thuja occidentalis tree is completely natural. During the winter months, sometimes the leaves of the tree will yellow or brown naturally. The brown from this occurrence does not look reddish or dry brown. The leaves may appear slightly yellowed, with brown hints. However, when bent the leaves will spring back quickly and show signs of moisture. If the leaves do not return to green when winter is over, then a more serious problem is at hand.


I would wait and see what happens--it sounds like the tree will grow out of the browning just fine.