Hello Elissa

There could be several reasons for your arborvitae to turn brown. How long has this browning been happening? Did it just occur? How close are the trees planted?

It could be that there is not enough air flow between them. I don't want to encourage you to remove one to allow for air flow but if you should replace them keep that in mind. Watering is also important and they should be watered at least once a week if there has been no rain. There was a period of time during July when it was very hot and they could have become stressed from the heat. Lack of water could be a main culprit for the browning of the needles.

Water well before winter and mulch generously at the base of the trees but make sure to maintain a distance between the mulch and the trunk of the tree. There is not a lot you can do to reverse the browning but the best thing is to wait until next year to see if they recover. And if they do, maintain a weekly watering schedule for them.

All the best

Rose Unes, MGV