"Residential neighborhood and not a garage"
Now that's funny. There are communities that have restrictions, but you would be told them before you moved in.
I really doubt a power washer, or watering your plants is a cause of his "wet basement." He needs foundation work. And that is *his* problem, not yours.
And unless he is paying the costs of running your vehicles, then what you own is not his concern.
I had the same problem with some retired bozo who didn't like the fact I bought a Z4. Until I got in his face.
To cut it short, the guy is harrassing you. What I would do is start filing complaints. It may have little effect at first, but if nothing else, he will be the first person they look at if say your plants disappear again. And just maybe, the cops will get tired of coming over and set him straight.
You'll probably need a restraining order in the end. Afterall, you have the right to live on your own property in peace. But not at the expense of living under your neighbor's thumb.