If you want the tree to top out at 5’, I think you really want a shrub. You might enjoy a slow growing ornamental tree , such as some Japanese maple varieties, but it would be a travesty to submit them to hard pruning. They are best allowed to be left to their own graceful natural form.

Maybe May pole apples? Or, I have a blue hibiscus that will top out at 6-8 ‘ with a narrow form, something like that could work without need to be always pruning. Look at some yew varieties, there are some with a narrow form that will work with your lay out.

I had to look up Magical Globe birch and I see it is a Betula pendula form grafted onto B. utilis to make a lollipop standard. I'm not familiar with your climate but grafted standards are quite vulnerable and can be short lived. If you're happy to put in the training work some hollies make good lollipops. Evergreen and with winter berries, if you get the right cultivar.

Another small tree I've often seen in similar situations is Pyrus salicifolia 'Pendula'. While not a lollipop it looks good in a formal garden frame. But get plants with a good height trunk so they don't end up as stumpy heaps of foliage. Another weeper is the Kilmarnock Willow but again get tall trunks as they too can end up a dumpy, clumpy mound if they're too short.

There's a grafted standard form of the dappled willow 'Flamingo' which I often see around here. But it does need regular pollarding to retain the brightest coloration.

How about Tina Sergent crabapple?

If you want to maintain a monochromatic look, you could use boxwood.

I think box would look a bit boring since the hedges are already box. Also getting box up to a 5 foot topiary would be a big job, or if bought ready trained, an expensive one.

Though not evergreen one of my favorites is a tri color dappled willow tree.

Yes, that's the one I mentioned above, aka 'Flamingo'.

Floraluk2 Great minds😉

The willow is gorgeous, but I read its roots are known to damage nearby structures.

Another non- evergreen idea— Limelight hydrangeas are often available in nurseries as trained standards with a single thick trunk. But of course no greenery in winter.

This particular willow would not damage anything in your set up. They're away from any building, and they are small trees which do not have an extensive root system.

Doug, what tree is shown in your photo? I love it.

I should also ask, what do you all think of the possibility of the trees being a little taller than the walls themselves? Might that look very odd when walking in the yard adjacent to this area?

Also, what should we plant around the trees in the quadrants? I want something low maintenance and that is a perennial.

Doug's mock up shows wisterias grown as standards, a skilled and labour intensive job.

Hardy geraniums would make a good ground cover.

I think the trees would actually look better taller than the walls. I think they'd look rather underwhelming if lower than the walls.

Standard wisterias at Churchill's home, Chartwell. Woodyoak, who posts here could tell you about growing them.

How much taller than the walls is ideal? right next to this courtyard is a seating area, so the adjacent view is something to keep in mind. I’ll include a photo for reference.

Get some bamboos of different heights with flags on top and move them around to see what you think looks best.

Smart idea! I will absolutely do that.

What about some lilacs or dwarf lilacs Unfortunately you live north of where they grow but camellias would do what you want and give you flowers.

One other thing. You patio looks similar to the area behind the arboretum and the Indianapolis Zoo, You are not that far a way for a day trip. Is there an arboretum or something similar to you so you could check what they are growing.?

Wisterias grown as trees are very impressive - but you shouldn't grow them unless you have understood what they need and are willing to do the work necessary to control them and get a good show from them. From my experience I prefer the Chinese ones. We have both a Chinese one and a Japanese one - I regret planting that one....! But we don't have any American types because they often don't have a pleasant smell. People in the neighbourhood - or even just passing through - when the wisteria are in bloom often stop to ask what they are! The Chinese one in May this year:

Look at photos of formal French gardens to get a feel for what might work.

Château de Pouy-sur-Vannes has a similar courtyard (albeit with fountains!) and the trees are taller than the walls, if I remember correctly.

Thanks. I love them and think this is a great option for our courtyard. In addition to staking them and yearly pruning, what is so complicated about them? Is there something I am missing? Thanks in advance.

cyn427, thank you. I'll look it up now. Boy, do I miss being in France (we were there this summer and i can't sotp thinking about it).

Revisiting this now. We can't seem to find Chinese Wisteria on a standard where we live, or even online. Globe Birch appear to be too small, so we are thinking maybe a crabapple. Any other suggestions? We'd like to get going on this fairly soon before options at the nurseries dwindle.

My husband wants to plant a black Tartarian cherry in each quadrant. Any thoughts on that? Thanks so much.

Check out Snow Fountain weeping cherry (serpentine).

Those are beautiful! he wants something that bears edible fruit, however.

Dwarf weeping mulberry ?

Looks like a very nice option! Im having a hard time finding them for sale.