Perennials for late season that will tolerate some shade:

Ajuga: Evergreen groundcover with blue flower spikes in spring. Many variations in foliage--both color and texture. 'Black Scallop' is a favorite for fall, with larger, very dark shiny leaves.  Makes for an exciting contrast with any yellow-leaved or -flowered plants--carex, black-eyed susan, gold mop cypress, to name a few.  Full sun to part shade.  Will do ok in shadier spots as long as soil is not too damp--but flowering will be greatly reduced.  Good deer & rabbit resistance.  Works as a gently trailing plant in a container.

Carex: A lot of breeding has been done with this thin-foliaged grass, resulting in some absolutely fabulous plants for borders and containers. Color varieties include chartreuse 'Everillo', (my favorite), green & white 'Everest', green and gold 'EverOro,' and bronzy 'Red Rooster.' Most are on the shorter side, under 18" high; some are upright, some mounding/cascading, and some are in-between.  Many are evergreen. Native varieties tend toward green or bronzed.  As grasses tend to be, they are deer and rabbit resistant.

Euphorbia: Wide ranging genus, which includes the poinsettia--all share the same milky sap which can be irritating to the skin, and showy bracts which surround the insignificant flowers.  Most will prefer full sun, but some benefit from shade in the hot afternoon climates. The most shade tolerant variety is E. amygdaloides var. robbiae--(Wood Spurge), which boasts green-tinted chocolate-bronze foliage with bright yellow-green bracts that emerge in spring and last for months. 

Heuchera (Coral Bells): So many heucheras, so little time......Breeders have gone nuts with this plant--there have to be as many heuchera varieties are there are hostas.  And that's not even counting the ones they've crossed with Tiarella to create Heucherella.  Mind you, I'm not complaining--my container gardening motto is "a heuchera in every pot."  Yes, they're that fabulous.  Some of them remind me of hoop-skirted petticoats--layer upon layer of large, lush leaves.  And so many colors--red, burgundy, orange, peach, yellow, lime, silvery green, black, purple, rose.  Some have veination in another color or a silver overlay.  And all will be happy with some degree of shade. Most are evergreen, clumping types, but heucherellas may be spreading depending on which Tiarella they are crossed with.  Don't mulch too close to the crown or plant too deep, and make sure the soil is well-drained--crown rot can be devastating.

Japanese Anemone: This one is definitely not planted as often as it deserves.  I think one of the reasons is that you'll rarely see it in a garden center in the spring (when most folks are shopping and  planting)--it doesn't bloom until fall, and plants out of bloom are rarely stocked--they don't sell fast enough.  Which is a shame, because it's a lovely and undemanding plant.  Smaller varieties are charming in a partially shaded bed; taller ones are simply spectacular massed on a woodland edge.  Recent breeding has resulted in shorter, more compact varieties which are easier to fit in the average garden. While still lovely, there's somehow a lack of grace that's found only in taller varieties, with blossoms nodding gently atop long,wiry stems.  But any Japanese anemone is worthwhile for the burst of color they provide when little else is in bloom.  Flowers are white or shades of pink, and may be single or double.

Cyclamen hederifoliumNo, these are not the fussy cyclamen you'll find at Christmas that need such exacting care. C. hederifolium, also called Hardy Cyclamen, is just that--cold hardy to zone 5 and relatively undemanding as long as the soil is well-drained and they get some shade.  Growing to about 4-6 inches high, they have the same shaped flowers as the holiday types, but only in pink.  A beautiful groundcover for a shaded woodland, and adorable with some afternoon shade in the rock garden.  They're a fine choice to bring some color to the area in front of your green azaleas for fall.  Dormant from spring to late summer, their silver marbled foliage is evergreen through the winter.  This gives you an opportunity to plant annuals in their space for summer--be sure not to damage the corms while digging.  Be careful not to water the annuals so much that the cyclamen corms rot--begonias are probably a better choice than impatiens in this case. Squirrels and other small varmints do like the corms, but the deer don't bother the flowers or foliage.

Jack in the Pulpit (Arisaema triphyllum): Red berries in late summer and fall make this native exciting in the damp shade garden.

Monkshood (Aconitum)

Toad Lily (Tricyrtis): 

 

Shrubs for the late season garden:

Beautyberry (Callicarpa):  Bright lavender berries line the stems in late summer and fall.  A berry-laden bush is truy a sight to behold. Both native and non-native varieties are commonly found.  Depending on the variety and climate, these can act Save and publish as herbaceous perennials, dying back to the roots over winter and rebounding in spring.  

Blueberries:  One of the most underused shrubs for the landscape.  Blueberries will fit into your design just as well as any other deciduous shrub--maybe better.  Delicate white spring flowers are followed by attractive (and delicious) blue fruit in summer, capped off with some of the best fall foliage you'll find--bright red for weeks before the leaves finally fall.  Give them well-drained acid soil, and full to part sun.  Although they are self-fertile, planting 2 different cultivars with overlapping bloom times will guarantee a happy harvest.  A must in the wildlife garden!

Blue Mist Shrub (Caryopteris)

Camellia

Illicium

Loropetalum

Mahonia Soft Caress

Oak Leaf Hydrangea

Pieris