I don't water the lawn at all, ever. I have an acre and a half so that's out of the question. I wouldn't care if the lawn all died to be honest
I have occasionally watered the tree (like a handful of times over 10 years) when we have had drought like conditions and the tree started looking like it needed it. We do get frequent rain where it just rains a little and then stops, not enough to water anything just to wet the surface. I do have clay type soil here, southern Missouri. It is on the east side of the house so has some shade on it by 4 oclock or thereabouts. The tree was only staked for the first couple years when it was small. I have never mulched it because I have some daff bulbs planted underneath. We don't mow around it until mid June usually so that foliage has time to die back. I do have a mole problem in this area and I have tried many things to get rid of them, nothing works so far.