Something evergreen if possible, maybe Picea mariana 'Nana'.

Here is a link that might be useful: Google Pictures

Clethra has been a difficult, finicky plant for me. I'm currently working on killing my second one. I think it's a pH issue, though it hasn't responded to the heavy peat amending that the swamp azalea accepts. BTW, my pH is 7.2.

I'd look at a fall blooming perennial.

Clethra Ruby Spice has grown well for me, although I am in a warmer zone than you. I'm not sure how good it would be for a foundation planting though, because it leafs out late. It also suckers a bit from the roots. It blooms for about three weeks for me from mid July to early August.

Here's a photo of it in full bloom on July 24:
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It is fragrant and attracts bees. I think it's a mid-size shrub not small - about 5' x 5' with a little pruning. It's a nice yellow color in the fall, but not spectacular.

My best shrub for fall color is fothergilla Mt. Airy. It is one of my favorite shrubs - looks great spring, summer and fall, very low maintenance.

In November 2006 it was bright red:
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Last November it was more yellow:
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It also has strongly honey scented flowers for a couple weeks in April:
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It's supposed to be hardy to zone 5.

Some asters might look good too.

Juliet

Here is a link that might be useful: Fothergilla Mt. Airy info at Dave's Garden

Notice the variation in coloring shown here and that the ones showing a nearly red flower on this page are all .com sites. Hyperbole, or something else? Differing responses to cultural conditions, including weather? Inferior seedlings being sold in its place, as seems to have happened with 'Rosea'?

Here is a link that might be useful: Google Pictures

Nice yellow fall color on my Clethra 'Ruby Spice'.

My 'Ruby Spice' is not a strong red in flower (more toward pink, but it doesn't fade out either), nor does it have wonderful fall foliage. It does slightly sucker, but the suckers are easy to dig up - I pot some of them and toss others, depending on if I think I can find a spot here or someone to give it to. However, it is attractive, if a bit late to leaf out. I have it in all day sun, facing SE, in a raised, added bed in front of my porch - it grows about 4', maybe a bit more.

I think I would be reluctant to have it as a front-of-the-border plant, though - it is late to leaf and it is a bit leggy for me - which may owe more to the perennials surrounding it than its native habit, judging from the above photo!

A better plant for you may be the Fothergillas, or what about one of the evergreen azaleas - I think there are several that would be hardy for you - many of them have foliage that bronzes in winter (it goes back to green with spring). If the Encore series is hardy, you would probably get 2 seasons of blooms. Iteas might be better looking than the Clethra - for me they are a bit smaller, and there are several with spectacular fall foliage ('Henry's Garnet' and "Saturnalia' come to mind) - the flower shape is similar, if smaller and more drooping, and white. If you really want an evergreen, there are any number of different, variegated, conifer species/cultivars that stay smallish, and which have colorful foliage.

You could also try a colored-leaf shrub, such as one of the variegated Caryopteris (there is another beside 'Worcester Gold', but I forget the name), with late season blue flowers, or one of the variegated Spireas ('Goldmound', 'Limemound', etc.), with pink flowers in summer. Both will stay 2-3', and can be kept in check by pruning out a third of the stems annually, after it has grown enough. An Abelia, one of the smaller cultivars, could also be good - white or pinkish, summer flowers on arching stems, 'John Creech' is evergreen here.

I would avoid most of the barberries, as almost all the ones around are developed from the basic Japanese species, and it has proven invasive in the SE. Pity, because there are some very nice garden forms....

I also wonder if another shrub might be better. I have C. 'Ruby Spice' planted in wetlands and along a woodland border I have C. 'Sixteen Candles.' My C. 'sixteen candles' is shorter and has white flowers, but is of southern extraction, and in the long run I'm not sure if it will be hardy enough here. They are nice plants, but I also prefer my Fothergilla 'Mt Airy' for all season low-care beauty. Juliet's pictures are good for giving you an idea of what the plants really look like. I'm afraid that Dibbit has suggested some wonderful plants that may not be hardy for you, like Itea. I tried Itea 'Little Henry' a few years ago, and it just wasn't quite hardy enough here, dying back to snow line each year until it finally gave up trying, so depending on the particular cultivar and exactly how cold your area gets (though your zones are similar to mine) you might find that Itea isn't hardy enough for you. Likewise, in my experience evergreen azaleas and Caryopteris may not be cold hardy enough to thrive and bloom though they might just hold on. I don't think Abelia is hardy enough for the zone 4-5 border either.

I like the idea of something that will be green in the fall to contrast with the burning bushes, and an evergreen as BBoy suggested would give you winter interest to contrast with the tan grasses (if you leave them over winter.) Some bulbs or spring blooming perennials and some late summer or fall blooming perennials (aster, goldenrod, etc. ) would extend the interest a bit longer, and you could even plant a type 3 (cut back over winter) clematis to grow up through the burning bushes and bloom in summer so you would have a garden with something going on in all seasons.

Harrison Flint, in Landscape Plants for Eastern North America, lists caryopteris as hardy for z.4a. He does say it may be winterkilled, but that it will come back from the roots and flower anyway - the usual cultural practice/suggestion is to cut the various cultivars of caryopteris to the ground in spring anyway, to keep them from getting too leggy.

He lists most of the various spireas as hardy to z.4, some as hardy to z.3.

Itea is listed as hardy to z.5a, so might or might not be hardy for the OP - it does like a moist, slightly acid, well-drained soil. And abelia probably IS to tender for the stated zone.

There were, when I googled, several "families" of azaleas that were listed for being evergreen and hardy for the stated zone, so I included them - I didn't see the "Encore" series listed so said they might not be hardy. I don't live in the colder zones (anymore, and not for over 30 years) so will bow to experience.

My Clethera 'Ruby Spice' struggled as a foundation plant (lime leaching from the foundation?) so I moved it last year and it is improving. My Fothergilla gardenii, however, flourishes there. You may also consider a small conifer as bboy suggested.

tj

I happen to have a fairly good shot of my Ruby Spice and Burning Bush in fall color together. Not a bad combo, but both are pretty big plants. I really like Clethras for their fragrance(who wouldn't) but quite frankly I like their suckering habit less every year.

BTW, very nice pictures Juliet! Your Ruby Spice looks happy!

Heres my RB/BB combo from October 30, 2006..........
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I need advice. I have what used to be a large clethra ruby spice in my yard. This fall, I had someone helping me in the garden. Unwittingly, when it was fairly cold outside (in the 40's) he pruned way back my clethra ruby spice. Now, there are no buds coming out. I cannot tell whether or not it will survive. When should I start to see buds, etc.? Please advise.
Thank you,
b ps
I live outside of Washington, DC

bggrgl, they leaf out late. Scrape a stem with your fingernail, if it's green underneath the stem bark it's still alive. Shrubs in general will resprout after partial or full cutback.