Tree advice needed

We have London Plane trees and they're starting to drop leaves. They also dropped leaves last spring and summer. This doesn't sound right. Should we...water more? fertilize?

 

Normal, especially as the weather gets warmer. LPTs need several years to longer to develop a deep enough root system to reduce heat stress. Watering more may help reduce the loss of leaves.

LPTs are very hardy trees.

 

Thanks! These are 11 year old trees, but they don't seem super healthy. I will try watering them though.

 

Hard to tell without looking at the tree, but have you checked for Bagworms? Those nasty little things nearly killed my tree in the front yard last year. They use your leaves as cocoons for their eggs, hence the name. If you do have them, I recommend you get some "Bacillus thuringiensis" as it's basically the only thing that kills them. It's organic and has no effect on mammals, and it works much better than toxic chemicals.