Shade, wet, tall, color. Astilbe? I am not sure how much wet they like, but they do like it somewhat wet. I just leave the flowers up all summer, fall and winter. They look nice even when the color is gone.

Here is a link that might be useful: Astilbe, first ones I found.

Goatsbeard?

Ostrich,royal, interrupted, cinamon ferns.. all like wet shade. All get pretty tall too

Paula

Hydrangea. They like to be watered a lot, so may do fine in that spot. They don't need direct sun at all, but would flower better with some bright light. (You didn't mention trees.)

Lots of kinds of hydrangea. Nice green foliage, summer blooms, leaves turn color in the fall, and flowerheads left on the plant look interesting in the winter. Endless Summer or another kind that blooms on new wood would be good for your area. I think they would freeze to the ground each year.