London Plane Tree yellow leaves
I have a London plane tree that I planted early in the spring this year, and it's about 15 feet tall. When I first planted the tree, I dug a hole twice the size of the root ball, and mixed about 20% mushroom soil with the soil I pulled out. The soil is primarily clay. I never mulched the tree, but I keep the area of the base weeded as wide as the hole was. Watering, I water infrequently, about every five days, more if it rains, and I trickle the hose for a few hours.
Right now it's August 11, and here in Southeastern PA it's been hot, but not too hot, with highs in about the mid 80s, and while it's been raining, we haven't had any extreme amount of rain. I did my routine watering on Saturday, 5 days after it rained and the soil looked really dry. Today, I looked at the tree and it's almost completely yellow and leaves are falling off. It primarily seems to be smaller leaves and leaves closer to the tree. I attached a picture, but it's a bit hard to see because other trees are in the background. I don't understand the issue because the trees under the same conditions it's done so well in all season