Paul Farhi covers media for The Post.

Good fences make good neighbors, or so the saying goes. But what happens when the fence is smashed by 35-foot-tall trees? How are the neighbors then?

The mini-monsoon that blew across the Washington region June 29 left its mark on our neighborhood — and on our back yard. We awoke the next morning to a bewildering vista. Three massive trees had toppled in the storm, torn from their roots. Two were arrayed across our back yard, the treetops pointing directly at the back of our house. The third had fallen diagonally across our yard and into our next-door neighbor’s property. The upper branches came within about 15 feet of their house.

We were lucky. No one was hurt. No houses were touched. No power lines were affected.

But we had a lot of cleaning up to do. That weekend, an enterprising tree-removal representative let us know how much cleaning up we had to do: $2,600 worth. And that was just for chopping up the wood. Hauling it away was our problem.

Picking my way over and around the giant oaks, I noticed that all of them had been standing on the property immediately behind ours. They were part of a small wooded area that separated our abutting back yards. In other words, the once-towering trees had been on our neighbor’s property. As the trees fell in the storm, they obliterated the split-rail fence that divided our property lines.

Cleanup, it now seemed, was a mutual problem. Their trees, our yards. I went to my next-door neighbor and proposed a solution: The three of us — my next-door neighbor, the across-the-back-fence neighbor and my family — could split the cost of clearing up the trees. No blame, no pain.

My next-door neighbor hesitated; she offered to go her own way, bearing the cost of removing the tree from her yard. I insisted that we pool resources. She sounded amenable, and we left it there.

But the third neighbor, from whose yard the trees had come, wasn’t playing.

I rang his doorbell and got no answer. I wrote a brief letter, requesting contact, and shoved it through his mail slot. No response.

I left a second letter on their doorstep. This time I got a call back.

After a few pleasantries, I outlined the situation and proposed sharing the cost.

“Well, I’ve been looking into what the rules are,” my neighbor said. “This is all new to me. And it seems [the law] is if your tree fell in my yard, I would be responsible for it. So the same rule applies to you.”

He was correct. Under Montgomery County’s regulations, and our insurance policies, a fallen tree is the responsibility of the property owner on whose property the tree falls, not the owner of the property whence the tree came. Play it as it lays, as it were.

But I suggested this wasn’t about the law or regulation or insurance policies.

“If my tree were in your yard right now,” I replied, “I would offer to split the cost of removing it from your yard. It seems like the fair thing to do.”

“If it was my responsibility, I would do it,” he said. “But in this case, as I understand it, this is force majeure [an act of God]. It’s not my responsibility.”

I tried to appeal to his sense of community, to shared burdens, to the common good. “We’re all in this together,” I said. “Don’t you feel any ethical obligation to your neighbors? What if you needed my help someday?”

“At this point,” he replied, “I’ll just stick with my position.”

And that was that.

Ignore, for a moment, the self-interest in my appeal, and consider this: Aren’t we our neighbor’s keepers?

Two of us said we are. A third said no, shifting the load to the other two.

Clearing some fallen trees is a small thing. But there’s a larger thing here, too. In the abstract sense, neighborhoods are really an agreement among people to live by certain rules and codes, some of them unwritten. So are cities, states and nations.

There’s another old saying, about a tree falling in a forest. In this case, a falling tree made a noise and did some damage, but not in the physical sense.