I have some late blooming astilbes that look great with the blooming hostas. Toad lilies are one of the last things to bloom in the shade for me. Also turtlehead, some daylilies, blue lobelia, perennial geraniums, and some asters are shade tolerant. Annabelle hydrangeas are just about to start (early this year!), and will bloom all summer. Woodland poppies have bloomed already, but will put on a second show in late summer. I fill in here and there with shade annuals such as tall impatients.

I go out of my way to find hostas that bloom in late summer as well as astilbe. Toad lilies, turtlehead, rattlesnake plantain (native orchid), and white woodland aster (also native) are the other plants I have/want to get that bloom in the summer-fall. I also have an Incrediball hydrangea which is an offspring of the Annabelle hydrangea.

Other than that I like a wide mix of foliage including hosta, ferns, dwarf conifers, ginger, and heuchera. I'm itching to get some Japanese Hakonechloa grass too. The conifers are my new favorites though because they are evergreen. It can be hard to find ones that do well in shade (they need a min of 4 hours usually) but it's well worth it.

Heucheras have nice flowers but their foliage comes in pink, purple, caramel(also the name is caramel) and many other colors. Astilbes are starting to bloom here but it is my first year with them so not sure quite when they bloom in our zone normally.

You know I also saw some flowers called manderin lights azeala in some pretty deep shade in my town. I know they come in other colors but you could try them.

I have two acres under 50 year old oaks, heavily wooded lot. I have plots all around my home edging the lawn. I have some color all season from March with the crocus to fall with berries on many woodland plants. My Jack-n-the pulpits have red berries for color. Hydrangea add color, autumn fern, but in my 3/4 zoned garden they are not hardy. My creeping jenny and garden primrose are pretty yellow right now. Perennial geranium is color--purple. The foxglove will be color, many annuals will add color, begonias, impatient. Day lilies, iris bloom for me. Autumn Joy sedum blooms for me in light shade. It can be done,color all season. I have all the already mentioned plants also. Check out some of the wild flowers. Early spring there blooms a tall garden phlox like plant I acquired from a neighbors land last year. I love it. Bottom line there are many options for you!!

I know it's an old standby, but I tuck in small groupings of bright impatiens here and there for some sustained color over the summer.

My absolute favourite as of last year is Masterwort. They come in different colours (red, pink, white) and mine have just started blooming and will go easily until September. I planted a small clump last year and this year, they are easily the tallest thing in the garden with a beautiful 2.5' mound of leaves with the flowers up another good foot above that. They are looking stellar with the Astilbe right now.

Thanks for the suggestions - the Masterwort/Astrantia is a great suggestion. I put some in this spring in a slightly sunnier location (4-5 hr. sun), and if it does well there I will move some of it into the shadier bed (2-3 hrs sun) and see if it will work. The bed maybe to dry for it since everything has to compete with maple tree roots, but the Ligulara is still healthy after 3 years so it should have a chance.