What grows in a Shady patch
 

I have at the back of my garden a patch where little grows on it. It has
trees above, the lawn gets patchy as one goes furhter.

(i) If where the grass grows patchily, if I put some turf down in spring is
it likely to stay? I've tried seed (including shady) but not much joy.

(ii) For the shadiest bit, I'd like some sort of shrubs that will grow as
fast as possible in shade and to a good height, eventually over 8foot?

(iii) Suggestions for perennial flowers, colour in the summer, in semi
shade?

Your help would be appreciated.

Colin