Leyland cypress branches turn brown because of an infiltration of three types of fungi: seiridium, bought, and cercospora. These three fungi enter into the tree during the summer months when the heat enlarges the tree’s stomata (pores on the leaf) and allow entrance of the fungi.Click to see full answer. Also to know is, what causes a cypress tree to turn brown?Damage to these trees can occur in the winter, however, when dry, cold winds draw moisture out of the tree’s leaves, causing them to turn brown. Reflective sunlight on snow can scorch leaves, also turning them brown.Additionally, what is killing my Leyland cypress? Cankers and needle blight that kill off portions of the tree frequently ail Leyland cypresses and often times lead to its untimely death. The shear amount of Leyland cypresses in the landscape has caused these deadly diseases to spread like wildfire, killing many trees. Keeping this in consideration, how do you know if a cypress tree is dying? How to Know If a Cypress Is Dead Examine the Cypress tree’s bark. If the bark has a brittle texture and is falling off in large chunks, the Cypress tree might be dead. Look at the tree’s limbs. Break off one of the branches at the bottom of the tree. Examine the needles of the Cypress Tree. Examine the tree trunk for large cracks. Can a brown evergreen come back?Whether needled or broadleafed, both evergreen trees and shrubs can look sickly and brown in spring, especially after a particularly cold or dry winter. Though there may be some branch loss, most brown evergreens do come back as spring progresses.