Chestnut Oak: Many Leaves Suddenly Turning Brown in mid-August
We have a mature chestnut oak in our backyard and greater than half of its leaves have abruptly turned brown. This was first observed about seven days ago and while I don’t have an exact timetable, I think that the change occurred quickly, perhaps over the course of a week. In the attached pictures, you can see that the trunk forks into three main branches. The leaves have died on two of those branches, while the third seems to be unaffected. It may be difficult to see the brown leaves in the photo: they have started to dry & curl over the past few days, so they don’t stand-out against the bright sky. The bark all around the trunk appears solid & intact. Some background: - Assuming that the tree was planted around the time that our house was built, it may be around 75 years old - We have lived here for two years & never saw any obvious signs of distress or poor health. - No fertilizers or herbicides have gone into our yard while we have lived here. Nor have there been any heavy equipment or vehicles in the yard. - The tree grows from a hill with a grade of around 10% (eyeballing it). - In October 2016, I built a small retaining wall to protect a garden about ten feet downhill from the tree. The structure's total height is ~2 feet... and that includes four posts anchored 12" below ground & set with concrete. While building this wall, two or three roots were severed: each about 1-2” in diameter. I assumed that they came from this tree, but not certain. - Within 10-20 feet there are two other trees of similar size: a white oak & another chestnut oak. Both appear to be healthy. I hope that there is some treatment option that could save the tree. Or perhaps I’m overreacting & the sudden appearance of brown leaves isn’t cause for concern. Either way, your expertise would be much appreciated! -
Dead branches and dead leaves are never a good sign.
We have been getting many reports of mature trees dying. Many have been chestnut oaks, where no pathogens, insects, or diseases have been found. Climate change and drought are suspected. The loss of some of your oak's root system when the wall was installed could have been a tipping agent, but it's impossible to say for sure.
We'd recommend that you have a certified arborist assess it. Use an arborist certified by the International Society of Arboriculture (ISA). Most are associated with tree service companies, and often come out and look at tree's at no cost. You can find one near you by following the prompts on their website: www.isa-arbor.com
Here is our webpage about making decisions when you have failing trees: http://extension.umd.edu/learn/how-do-you-decide-when-remove-tree