I did not know that! Thanks.

Some of it is dependent on soil, trees in well drained soil will have deeper roots than trees growing in very moist/wet soil.

Also, not all oaks are the same, the "bottomland" oaks like Water oak or Willow oak typically have shallower roots than upland oaks like White oak or Northern Red.

I'm guessing these were Northern Reds, based on trunk bark and leaf shape. I have been mulching moderately on one side of them (3" wood chips and shredded leaves every year or so), and letting nature take its course on the other side. They were growing on the high side of an 18" retaining wall left over from ages ago. The underlying soil is mostly clay, so maybe there was insufficient drainage. The two remaining (and beloved) oaks are the basis of my primary garden. I can't stand the thought of losing them. The photo below is from 2011. These gardens are now filled with hostas.

I think you may be overthinking this. Yes, any object suspended up in the air has the potential energy to come down. That's 7th grade science....or was it 6th? But your trees are almost surely just fine. I can't account for the failure of those other two-this is a rather rare event-but in general, trees are not just falling down for the hell of it.

Handsome trees

Thanks to you both. Wisconsin: your encouragement is MUCH appreciated. I love these trees, and my neighbor has just cut down a mature pine forest next door (much of which fell into our yard, demolishing part of our fence). He even cut down a gorgeous Japanese red maple in his front yard. It's breaking my heart.

LOL!! Neighbors with chainsaws.........that should be something that is disclosed when you purchase a house. How many chainsaw-happy neighbors there are in the area and what mature trees can you expect to be their targets?? Some folks just don't get that mature trees ADD to the value of a property, not detract from it.

Hope this guy cleaned up the mess he made on your property and offered to pay for the fence repair.

He's the new neighbor. He was sure the trees would hit his house, though once the nearby trees were down, he kept going. (He has offered to fix the fence.)

here's hoping for a hot summer in Mass. He'll learn his lesson quick

How is it-and this seems to be happening more-that people will buy a house and only then, once the paperwork is signed, realize there are these big scary things all over the lot called trees? What's going on? I get it if the trees have grown more than expected-not everybody is tree-savvy-but that's not this. What's going on? These Houzz forums are all about neighbors taking down trees-lots of trees-lately. From the Florida board to this one, that's half of what I'm reading about lately it seems.

Tom, I'm just making some assumptions here but this is my take: lots of these chainsaw-happy folks are new homeowners (or new to suburbia) and unfamiliar with either landscaping or gardening at all and are not, as you say, tree-savvy. And they have read or been told all those horror stories about large trees on their property - they will fall and destroy the house (not necessarily true), their roots will invade and damage the foundation (also not necessarily true and far less common a situation than one would imagine) and you can't grow anything under them or even in close proximity (again, not necessarily true). They consider this and determine the only viable course of action is removal. Out come the chainsaws!!

Of course, the more reasonable alternative is that after purchasing a new home, they have visions for the landscape/garden that don't include a heavy population of trees. But that doesn't exactly jive completely with the wholesale removal of anything on their property that grows taller than 10'.

I think some folks are just plain scared of large trees. Period. If that's the case, do not move to the more suburban or rural areas of the PNW - big trees (and I mean BIG) are extremely common in virtually any garden. And depending on area, removal during the construction phase is done only by permit, is closely monitored and in some cases, removal of any existing native trees must be followed up with a suitable replacement.

I don't see anything to disagree with there, gg! People are becoming wimps! Like my friends that wouldn't let their little boy play in the woods because well, you know-poison ivy! Not that there was any of it there...or that these two adults would have a clue what the plant looks like. Just "playing it safe" which is to me a form of very slow suicide. Mental suicide in this case. Poor kid. He's probably half grown up now and ready to be afraid of everything. Imagine if, horror of horrors, the kid would have contracted a case of dermatitis! He might have learned something. Can't have that.

Now what were we talking about? (With an lol at the end).

I'd say that you all have my new neighbor pegged.

It has become a common "type", I'm afraid. Fear is by far the most common and easily misapplied human emotion, capable of making seemingly sane people do incredibly dumb, callous, or despicable things.