Try Hesperis-It's a nice perennial that can get some height to it.It grows like a weed here in CA.....
Also,Acanthus is very impressive for the part shade with big bold leaves and pretty flower spikes.

Hesperis is a weed and banned in CT. I have never seen it get 6 ft tall. I don't think Acanthus is hardy here. But thanks for the suggestions.

Filipendula rubra, Aruncus dioicus, Aconitum carmichaelii all will love and grow tall in described by you conditions.
Actaea racemosa and Chelone glabra 'Black Ace' also could/may attain 6' in a such conditions.

Acanthus mollis is exotic annual even in 6b CT probably due to the wet winters as well :-(

Thank you ego45. Those are great suggestions. I actually have an Actaea arriving soon and the Aconitum. I was planning to put the Aconitum in a sunnier bed but will reconsider that. I never heard of that Chelone but it looks like a great choice.

Some of the thalictrum get that tall and should be hardy for you there -

t. delavayi Hewitt's Double, t. rochebruneanum are l-o-n-g blooming at close to 6-7', along with another purple flowered t. delavayi I grow that I bought with just a collection number and not named - wouldn't be without it.

That's another great suggestion, morz8. Another plant I loved in a previous garden long ago.

Lobelia(cardinal flower) Some get 3-5 feet tall.

Mor, does t. rochebruneanum need staking with its height?
How it is holding in the rain?

Oriental Lilies, especially pastel colored, will grow in partial shade.

Eupatorium purpureum (Joe-Pye weed) might work there.

-Caroline

Yes, in my coastal wind, thalictrum rochebruneanum does need staking - I have a lot of organic content to my soil but I'm not sure it would not need it in less fertile ground. Foliage and flowers don't seem fazed by either summer rain or our dry early fall either one, but my beds do get supplemental water - when and if it quits raining :)

It sounds perfect for clematis, no? They love shady feet.

Lots of exciting suggestions. What great folks there are here. I have planted one clematis. I just don't know if it will get enough hours of sun, though the shady feet part is there. We'll see.