I have grown bleeding hearts. They're easy. A friend of mine has grown Japanese forest grass successfully in part shade.

It sounds like you're interested in tall groundcovers for shade. Some taller ones include trollius, mondo grass, lady's mantle, foxglove and toad lily.

As for when to plant them, I would avoid planting them before spring in case you get any hard freezes between now and then. If your area never gets hard freezes, then it might be all right to plant them now. Be sure to mulch them.

Here is a link that might be useful: Shade gardening