I'm a great believer in “The right plant in the right place”.
Bearded Irises need as much sun as you can give them.
They hate cold wet feet in winter. So don’t plant bearded irises under a tree, or in that damp spot where nothing seems to grow. Have a look at some of our Siberica and Ensata iris, they will cope with wetter soils and a little shade, some of the Species iris as also worth considering.
They need a South facing spot, such as at the bottom of a wall in a dry soil.
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.