They give a good large clump, rather than just 1 piece. All the plants I have mentioned like well drained soil, not wet. Perrenials that grow in mostly shade. They make a really lovely low border and do well in heavy shade. Also available is one with pink flowers.
Hellebores are fantastic understorey plants for shady spots.
The Helleborus X Orientalis is a good one of them, grows easily and is showy in winter. It is nice to use this as a center point of the shaded area and plant other items around it. Another shady type plant is bee's balm. Perrenials that grows in full sunlight. Perrenials that grow in mostly shade.