Posted: 18/06/2013 at 13:59
First of all, can you remove a few of the lwoer branches of teh trrees to allow in more light and, more impirtantly, more rain as the ground will get very dry under trees.
Then have a look at forms of brunnera, lily of the valley, geranium macrorhizum, pachysandra, ferns such as Polystichum setiferum and the dryopteris group, pulmonarias and vinca minor, especially the alba form with white flowers that will show up. bees will love teh geranium, lily of the valley and pulmonarias.
Variegated ivies can also be used as ground cover in full shade but will, when settled, head up thetrees to teh light as they mature. They do make excellen hosts anf food for insects when they are mature.