I have bearded Iris growing among my daylilies which are in dappled shade once my flowering crab. leafs out. You may also want to try something like Hydrangea Annabelle - quite tall with beutiful blooms but different foliage.

If you like the idea of iris (so do I), there are several others than bearded ones you could try. Yellow flag (iris pseudocorus) loves shade and has stunningly good and tall foliage. It also likes moisture, and when it gets it, it spreads. However, it is easy to keep in check by cutting back the clumps once a year. There is a purple form (versicolor, I think) that is also very nice, though the foliage is not quite as tall as pseudocorus. And then, my very favorite is Iris Aichi-no-kagayaki. It is a hybrid between pseudocorus and ensata. It has chartreuse foliage, which is why it's my favorite. It blooms yellow. Something blue with it is stunning. I know that plant delights nursery carries it, though there may be other sources too.

Chasmanthium latifolium (wild oats, northern sea oats).

This is an outstanding plant and does well in shade - and can take dry shade to boot once established. While it is a grass, it doesn't look "grassy"; rather, it's reminiscent of bamboo.

It gets about 3-3.5' and shape is upright/slightly vase-shaped. It is particularly lovely when it blooms. This grass gives great winter interest, too.

Iris pseudacorus is a no-no plant here - on the invasive species list and responsible local garden centers no longer carry it. Depending on the amount of light this area really gets - 5-6 hours of dappled sunlight is fine - I'd suggest a NZ flax, Phormium ctv. It will provide the upright structure you want with iris-like blades and offers a taller presence than most other shade tolerant OG's. And it comes in a whole range of colors and is evergreen as well. Quite tolerant of drier and semi-shady conditions.

Fantastic suggestions, thanks! I really really like the Chasmanthium. Do you think it's bamboo-y enough looking that it wouldn't look out of place near the cannas? Do birds like the seeds? How is it with the self-seeding?

Phormium looks really great too. How have I not discovered it yet? I'm not sure it wouldn't look kind of stark in the winter (basically the only evergreen plant in the bed except for some epimedium that's going in this season). The Chasmanthium seems to have a softer-edged form.

I think Chasmanthium would look fine with cannas. It does self-seed, but I don't consider it invasive in my yard.

Only one more thing about the Chasmanthium. Anybody with dogs have it? I read someone at DG saying their dogs love to munch away at the new shoots. I have a big lab mix and the last thing I need is her tromping through to the back of the flowerbed for a snack!