I have 40 ft bald cypress that is not leafing properly. Many of the branches are dead. I think I may have poisoned it when I built a bench surrounding it, for the legs of the bench I used treated pylons. Is it possible that the toxins from the pylons have leached into the ground and poisoned it? And, if so, if I remove them, can the tree come back? There is some budding occuring but it is too late. Is size relevant as to when cypress start to leaf? Other smaller cypress trees in my neighborhood are blooming nicely.
You may well be right about the treated wood affecting your tree. Here's an article that might help you with ideas to save it: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/contaminated-soil-treatment.htm
If you want to get a soil test, here's a link that will help you locate the nearest extension service: https://www.gardeningknowhow.com/extension-search/