Redwood trees are large trees and a lovely addition to many landscape settings. These trees are susceptible to browning because they are deciduous conifers that lose their leaves each fall and grow new leaves the following spring. Drought or disease can also cause browning of redwood foliage.
Winter injury or frost injury is a common cause of browning in redwood trees. Early fall and late spring frosts can cause redwood foliage to turn brown or black. Winter injury may only affect small portions of the tree or it can cause all of the foliage to become discoloured. Once winter injury occurs, there is no way to reverse the damage.
Drought stress is a common cause of browning of redwood trees. Symptoms of drought appear when more moisture is being lost through the foliage of trees than the roots of the tree can replace. This process dehydrates the leaves and causes them to turn brown. Drought can cause leaves to appear scorched around the margins, which can be either light or dark brown in colour. Drought stress symptoms usually begin at the top of the tree and move downward. Severe drought stress can cause all of the tree's foliage to turn brown at once.
Overwatering redwood trees can also cause browning of the foliage. Leaves often become discoloured beginning at the bottom of the tree and working upward when overwatering is the cause of browning. Leaves may appear mildly scorched, turning a light brown at the margins. Avoiding oversaturating the soil is best accomplished by allowing the soil to dry completely between irrigation. Wet the soil deeply at around 2 feet for best results.
Trees often develop sunscald injuries during the winter months, when the nighttime temperatures are very cold and the daytime temperatures are warm. The symptoms associated with this condition generally develop on the north side of trees. Redwood trees with sunscald often develop light brown or reddish-brown patches of bark. The bark may split or peel exposing the internal wood of the tree. Eventually, sunscald can kill trees if symptoms persist. Young trees are most susceptible to death from sun injuries because their bark is thinner than more mature trees.