People plant trees where there is no room for them all the time. And often when a non-gardener talks about a big tree "big" turns out to start immediately above head level. Two instances right there where a tree of much size may not be a good recommendation.

A tree should probably go everyplace a tree can safely b planted in my area. Out west, who knows.

Now far as recommendations, I own a 68 Mustang a 98 MarkVIII and a 97 Aurora. I DO NOT recommend any of them to my mother. Her situation is not right. Neither is every situation right for a tree.

Many posters ask for a tree that will not exceed some short, predetermined height - like 10-15 feet (or even smaller) - or want something narrow yet evergreen and flowering as well. There are very few trees that will fit under those criteria but a whole vast range of shrubs that will. And most shrubs have an ability to be trained or limbed up into a standard or single trunked form that act and appear just like a small tree. And most shrubs take to pruning to remain in size far better than any tree can as well.

It does the querying OP no favors to make suggestions of trees that are markedly unsuitable for a specific site due to the potential growth exceeding the specs when a shrub is really what they need but are not familiar enough or knowledgeable enough to know that is really what they are asking for.

Many (most?) urban and suburban properties are not large enough to accommodate more than one or two full sized trees. And not all that many of us have the acreage available to plant whatever trees we'd like. One cannot consider just the trunk diameter as the overriding factor - it is the mature height, canopy spread and the nature of the root system as well that must be taken into consideration. And most shrubs don't come anywhere near close to the space these other tree characteristics occupy.

"I've also long disliked how many sources don't clearly delineate the
difference between a small tree and a shrub. To me, there is a huge
difference between the places I want to put a single-trucked deciduous
plant that loses it's lower branches and a good spot for multi-trucked
shrub that keeps all of it's lower branches...but most online sources
don't clearly delineate between the two."

While the words tree and shrub may bring up two entirely different pictures in your mind, nature doesn't make that distinction. There is a continuum between what you seem to picture as a shrub and what you seem to picture as a tree. What you might consider a shrub, at one point, might well turn into what you would consider a pretty good sized tree, given a few years (decades). Plants that you call trees might well grow as shrubs in some circumstances. As Gardengal pointed out, many trees can be trained/encouraged to grow as a shrub-form plant, and shrubs can often be pruned/trained to grow as tree-form plants. It's very common for inexperienced gardeners to choose the wrong plant for a location because they don't realize how the plant will grow. People will sometimes read the "mature size" stated on a nursery tag and assume that size is the maximum size the plant will attain. Then, before they know it, the plant has outgrown that size and begun taking over their world.

Lots of older properties here have buildings crowded by trees where a foundation shrub was what was called for during the original planting.

"I've also long disliked how many sources don't clearly delineate the difference between a small tree and a shrub. To me, there is a huge difference between the places I want to put a single-trucked deciduous plant that loses it's lower branches and a good spot for multi-trucked shrub that keeps all of it's lower branches...but most online sources don't clearly delineate between the two."

Very true, but there are more than just single-trunked deciduous trees. Some, like yellow wood, I'm told tend to branch out fairly low, and can have a fairly large landscape 'foot print,' though considered trees. And some evergreens have to be limbed up if you won't want the 'Christmas tree' look, and thus can take a lot of yard space. Pin oaks are notorious for sending limbs angling download toward the ground (got 2 on the home & lot we bought, and they do).

And not all shrubs are wide, bulky things.

I'm simply saying the reality is a little more nuanced.

Richard.

"... I own a 68 Mustang a 98 MarkVII and a 97 Aurora." I DO NOT recommend any of them to my mother."

Excuse me for asking, but why is that? I'm a bit lost here.

My mother is older and only has room for 1 car. Her condo works for her, but not me.

The 68 Mustang as a daily driver should only be owned by folks who are either well off or like turning wrenches. It also is a liability in the snow.

The MarkVIII is LOW, and a liability in the snow.

The Aurora is truely Europen inspired, yes I am talking to you Volkswagon and Jaguar. It has engineering/design issues and while it moves in the snow also requires you to either love paying your mechanic or turn some wrenches.

Now for me, they all fit into what I do.

That's why I drive a truck and my Mom drives a van, right? ;-)

OK -- now I get it.