Wait a minute. Let’s back up and talk about the Tulip Poplar. Are you saying it is so close to the house that a shrub planted under it would block a window? That sounds worrying. Any chance of a picture?

deer?

most flowering plants require full sun .. and as you go into darker realms.. flower production falls ...

with so little light.. you will be lucky to get massive green growth to simply survive.. and the plant will struggle to bloom for fear of wasting too much energy ... which its lacking due to low light levels ...

also.. not unlike trees... shrubs dont stop growing at some magical height.. but with shrubs that is when the rejuvenation pruning starts .....

the under 3 feet will be your defining variable ... again.. because you will have to be aggressive with pruning.. which means.. you might never get a great flower show ...

how about a few pix ...

ken

I have several Pieris growing in deep shade and doing very well, they even flower regularly.

I did not expect them to do well, it's too shady but I needed to put them somewhere at the time and that spot was empty. They've been in that spot well over ten years now.

They're taller than you asked for but there are dwarf cultivars available.

They are evergreen and quite attractive even when not in flower.

Sweet box, Sarcococca species, is my first thought. It will grow quite happily in full shade, has very tidy evergreen foliage and blooms in late winter with small and somewhat insignificant white flowers but with a very pleasant, intense and carrying fragrance. A range of sizes are available but none get very tall. Quite drought tolerant once established.

“shrubs dont stop growing at some magical height.” Well, that is patently not so. There are plenty of low growing shrubs which will not exceed their genetically programmed dimensions. Otherwise we’d have forests of lavender and ling, etc towering over our heads.

But before mentioning any names I really thing we need to have a picture of the situation to judge exactly how much space and shade there is likely to be.

In retrospect, that might be a Saucer Magnolia instead of a Tulip Poplar:

https://www.thespruce.com/magnolia-trees-saucer-magnolias-2132135

It was here when I bought the house about 20 years ago, and the previous owners CALLED it a Tulip Poplar. But now I remember that we talked about it on here before, and I'm pretty sure that the conclusion was that it's a Magnolia.

I took this picture yesterday (Sept 21) at around 4pm, with me facing North:

I recently had a bunch of wild trees removed that were blocking sun on the Western side of the house (left of the picture), so the tulip tree that you see on the left was growing weird and is just now starting to fill out properly.

It's really way too close to the house, and I have to trim limbs back every year to keep them off of the roof. But it balances a dogwood on the Eastern side of the house.

This is a closer picture of beneath the tree:

I measured, the distance from the downspout to the tree trunk is 5 1/2 feet. It's hard to tell from the picture, but the tree-to-house line is a 90 degree angle to the foundation.

While I was measuring, I checked; from the ground to the window sill on the window on the right in the picture is 40".

There were a bunch of Heavenly Bamboo shrubs in this area when I bought the place, and last year I relocated all of them to open things up. You can see that I half-heartedly put in some plants with no real design in mind, I just followed the path that I created with mondo grass, coral bells, and hostas.

Now I'm thinking more along the lines of an evergreen shrub (maybe more than one) to sort of block the water spigot, hose reel, and sprinkler system that is there but you can't really see in the picture. Then I could move the hostas and coral bells to group together in front of that shrub, then layer outward into the sunnier area with flowers and sedum.

Looks like a fair amount of sun. Which direction does the house face?

tj

The picture was taken with me facing North, so the house is facing South. The porch blocks morning sun, then the tree leaves block from around 1pm until dusk.

You can see that the hostas closer to the house are good, but the two that are further away from the house are a little cooked. So I figure that I need a shrub that is good with about the same amount of sun as a hosta.

It's a deciduous magnolia but not a saucer magnolia, rather one of the many others with a different parentage. Perhaps 'Galaxy'.

Don't dig shrub sized planting holes where the magnolia roots are - the underplanting with comparatively small herbaceous plants you have been doing so far is the most suitable for a space directly beneath such a tree. With things like spring blooming bulbs in compatible colors being classic companions for early spring blooming magnolias.

Any suggestions for something shallow rooted that might help fill up the back area, close to the house?

Nothing is more shallow rooted than geranium nn macrorhizzum

Remember you also have to be able to get back in there to do anything involving the surface of the house. Including washing windows - putting a miniature shrub in front of the lattice to the left of the stairs and a significantly larger one near the corner of the house, beyond the magnolia in the second shot would do a lot to enclose the scene as seen from the second view without digging in close to the tree or blocking access.

Tour some local retailers to see what you might like. And can examine and buy in person. Instead of looking for suggestions from what often turns out to be thousands of miles away.

The problem with living in a small town is that EVERYBODY has the same plants! If you want to look unique, it can be a challenge :-/

Based on the info given, though, I'm leaning towards putting a few containers there instead of a shrub. I think it might be the only real way to get some color that I can surround with hostas, without it going too deep or covering the windows.