We purchased several arborvitae from local Mennonite’s. The trees are 15 yrs old and about 15 feet tall. They re turning brown. From what I read it’s not unusual. What are your thoughts? Also the trees are very tall and thin. Is there a way to make the trees fuller.
Schuyler County New York
Thank you for your inquiry, although I have seen this happen over and over with this plant. Probably the number one inquiry regarding this evergreen.
Transplant Shock or water stress
If a newly planted arborvitae (Thuja) develops brown leaves or twigs, the most likely cause is transplant shock, a condition that's caused by loss of roots when the plant was dug up -- it can last a year or two and might kill the plant if it's severe. Transplant shock can cause leaf scorch, a yellowing or browning of foliage, and branches might eventually start dying back. The best way to deal with transplant shock is to keep the plant well-watered (early in the day) for the first year or two. Ensure it gets about 1 inch of water weekly, including rainfall, especially during its first year, and add a 3-to-4-inch thick layer of mulch under it's canopy to conserve soil moisture. Overwatering can cause root rot that also can cause foliage to brown and die back, so water only when the top few inches of soil feel dry to the touch.
Hope this is helpful.