Causes of Emerald Green Arborvitae Turning Brown

Emerald green arborvitae (Thuja occidentalis) is also referred to as white cedar and is an evergreen with bright, emerald green foliage. The tree can grow up to 30 feet in height with a spread of 8 to 10 feet. The tree is used for creating screens and hedges and is easily propagated from cuttings. Emerald green arborvitae grows well in any ordinary soil and does even better in swampy areas and alkaline soils. The trees need full sun exposure and high levels of atmosphere moisture to grow optimally.

Exceptional Cold

Emerald green arborvitae is not very cold hardy and does not tolerate exceptionally low temperatures. If exposed to very cold temperatures, the foliage of the emerald green arborvitae is likely to turn a yellowish-brown color.

Damage to Tree

Emerald green arborvitae is likely to come under stress when its branches and foliage is damaged. This causes tissue death and consequent browning of the tree. When browning is seen in just a few areas on the tree the solution is to prune away the damaged limbs down to the healthy tissue and make way for new healthy green growth.

Root Damage

Root damage is another likely cause of browning where a root rot organism is possibly spreading through the root grafting. A change in the water table can also cause this where the roots are being excessively flooded. During winter, it is common for water or ice to accumulate in the tree roots. This hinders the water absorption of the tree where not enough water is sent to the foliage and consequently causes the tree to start browning.

Borer Damage

Insects like borers can also lead to the browning of the emerald green arborvitae. It is very easy to isolate borer damage by inspecting the tree where borer presence is evidenced by little round holes in the trunk of the tree. There could also be other bugs or rotting in progress in the roots, which causes the tree to brown.