check this tree out: https://plants.gertens.com/12070009/Plant/806/Sunburst%C2%AE_Honeylocust/

As I recall the honey locust trees in the DC area, they seemed to be heavily afflicted by webworms. What about serviceberry, crape myrtle, or dogwood?

River birch could work, but not paper birch (not sure which type you had wanted). Flowering cherry -- especially the Autumn Flowering ones, grow fast with not too dense a leaf cover. A native Persimmon would be fun.

Some variety of Cercis might work. I'd look for one more shrub/vase shaped then do some judicious pruning in it's youth to get the form I wanted. Green, gold, burgundy, variegated- lots of choices.

I love Cercis, but wouldn't the foliage be quite dense? Also could I control caterpillars on the honey locust with a yearly treatment? Maybe with injected imidacloprid?

I wasn't sure so looked up if injecting imidacloprid into tree trunks is safe for bees and pollinators. It isn't. The chemical will be taken up throughout the tree including leaves and flowers. Bees love honeylocust flowers, so (sadly) this would be a high kill area for them.

Other trees with sparse foliage: sweetbay magnolia, fringe tree. And mimosa -- which can be invasive so only plant mimosa if you can keep it in check.

Look again at your first choice, a birch: mgnv.org/plants/native-plants/trees/betula-nigra

Lovely tree, widely adaptable to conditions, fast growing when young. Eventually -- as in 50 years or more it might get too big for your site -- but I wouldn't worry about it for the first 40 years, judging from a couple plantings I see near me. Widely available in nurseries, too.

I can certainly appreciate not damaging pollinators. However, can't damage be mitigated by timing the injection after bloom? If not, I'll certainly have to take a look at the River Birch again

I don't think so ... once the chemical is in the tree, it can last a long time, over a year. So there's no guarantee that even next year's flowers are safe for pollinators. Oh and its leaves that fall in autumn will be toxic also. Really it's a chemical to avoid for home use.

Question is, how likely is it that your honey locust will experience a problem? We might be worrying for nothing! What you could do, is look for honey locusts in your neighborhood and just see if they look healthy. And, go to a reputable nursery that sells trees and talk to them about potential problems and options to deal with them. Then if you still like them, go for it! It might thrive and be a wonderful tree.

River birches do very well in Northern VA. It is native here and I have two. Chionanthis virginica (Fringe tree) is a wonderful tree that flowers in early summer and so is Amelanchier (Serviceberry which flowers in spring). Both are native as well and quite lovely.

I hope you will rethink using pesticide/herbicide applications. Plant native to attract birds as well as pollinators and the balance of nature will take care of most issues. Chickadees, for example, require thousands of insects (especially caterpillars) to raise just one of their young. We have several wonderful native plant nurseries in the area. Happy to share names if you would like.

What do you mean by "shallow" back garden? Soil is shallow or planting area is skinny? We used to have a honey locust. I don't know what variety as the previous owners planted it. But it grew fast to 40 feet and kept getting taller and much, much wider. It also had roots that protruded through to grass which made it a real pain to mow around. It did have nice, delicate foliage like you requested, though. Ours became infested with some sort of border and we wanted more sunlight and more space in our yard, so we opted to cut it down rather than treat it. One caveat - if you go get one, make sure you get the thornless variety.

Oops, borer, not border, LOL.

Given how tall the honey locust seems to get well probably opt for a river birch. We have one in our back yard that is infested with sawfly larvae and has lost about 50% of it's foliage. I just hope the new one won't suffer the same fate. The feces of the larvae cover our porch about 1/8th of an inch deep. So there is that concern...

By shallow, I mean our back yard is maybe 20-25 ft wide and then hits the property line.

Not sure how to deal with sawfly larvae in a non-toxic way. Birds are now really helping

Problem-free Trees for Virginia Landscapes | VCE Publications | Virginia Tech (vt.edu)

I've seen Carolina silverbell in a few yards, Halesia carolinium. Although they can get quite big (at least I've seen big ones) they grow relatively slowly. I had its smaller foreign cousin, Japanese silverbell in my yard, scientific name Styrax japonicus. I have also seen Yellowood, Cladrastis kentukea used as a landscape tree for small spaces. I also had a sourwood tree on one property I managed, scientific name Oxydendrum arboretum. Another common tall but narrow street tree I see around is Persian ironwood, Parrotia persica. Sometimes goes by the name Parrotia. Grown under the right conditions it can have stunning fall foliage. Another nice tree is Cornelian cherry, which is in the dogwood family but has lovely yellow spring flowers, scientific name Cornus mas. Some of these trees are a little hard to come by, but not impossible. I have seen most of them in big comprehensive nurseries or could be mail ordered.

If you're not living in an area with a big breakout of pests, I wouldn't shy away from a honey locust. Also, there are ways of keeping pests under control outside of imacloprid. It's really a last resort.

Our honey locust was at least 40' wide. Not a good fit for your shallow yard.

If you want a narrow tree, look for the "fastigiate" form. There are several honey locust cultivars with various characteristics including thornless and seedless. It is a fast growing tree, so therefore susceptible to a whole host of issues like weak wood. Its not naturally long lived, so depends on your time frame as to how appropriate it might be. If I was looking for a very narrow tree, I would not pick this, I would pick the fastigiate form of Parrotia persica. We had it in my former neighborhood in Allentown PA, it looked good. Or the aforementioned river birch, I have two on my property right now, they are tall but narrow especially if pruned. Or the sourwood, although that one is hard to come by . .

Growth habits of five cultivars of Gleditsia tricanthos (Honey Locust)

You also might be able to find a fastigiate and seedless form of Sweetgum, I have seen them planted around my town in MI and also found one at a nursery. Scientific name Liquidambar styraciflua. Nice burgundy fall foliage color. The species variety has spiky seed balls that some folks find to be a nuisance in the yard.

My five-year old River birch is already 5 feet wide. It does have a light canopy. What about Little Gem Magnolia? Would meet the height and width requirements. It’s evergreen and has pretty white flowers. Or an interesting redbud like those with golden foliage on a standard (single trunk)?