I'm a great believer in “The right plant in the right place”.
Bearded Irises need as much sun as you can give them. If your garden border is shady or too damp why not consider a different variety of iris. Many Siberica and Species Iris will grow in shade, Ensata Iris will grow in damp or even boggy areas and Louisiana Iris will thrive in the shallow water at the edge of a pond or stream.
Bearded Iris hate cold wet feet in winter. So don’t plant them under a tree, or in that damp spot where nothing seems to grow. They need a South facing spot, such as at the bottom of a wall in a border with soil on the dry side of damp.
Tip: Plant with the rhizome pointing to the South so that it is not shaded by its own leaves.
Tip: Planting a cluster of iris? Keep all the rhizomes pointing in to the centre of the planting, with the leaves in an outer circle. As the cluster grows, the leaves will move outwards, keeping the rhizomes in the centre, with as little shading as possible.