The shady parts of the garden don't have to be dull at all. There is a variety of shade loving plants with beautiful foliage and flowers as well. My beloved Hosta is one of them. There is really a wide range of Hosta plants: some have variegated leaves, the other come in all shades of green or blue-green.
I mixed Hosras with Alchemilla, ferns and Lyshimachia ciliata 'Firecracker' that has red foliage.
This Clematis too thrive in semi-shade very well. The flowers are really big; looks like 'Nely Moser' cultivar, but I am not certain of it.
Under the hazelnut shrub I grow Astrantia, Carex, Hosta, Tiarella, white flowered Dicenta, Polygonatum, ferns, Luzula sylvatica and Hostas.