11a Food crop in Germany that is universal, arriving from the East (6) D?U???
13a Young ladies gathering, mightily displeased (6) ????AD
35a Group of flowers grew around hole in one area (8) ?????E?E
Yes, tedsgran - it's a tricky gimmick and Ifor's really turning the screw with some of the downs (still, it's all thematically relevant and I think it works out nicely in the end).
Good luck with it.
1d drops 'e' 'cr[e]ating' to give the container indicator - add it to 'on[e]' in 23 [ad(eno+i)d - 'add' = 'put together'].
You're looking for a large slightly wonky diamond - title of the relevant work, in the shape of the work (9,3,10 letters).
10a 'could be' an anagram of NAS(t)IER 'over (t)ime' - for ARIENS born under that star sign in spring.
3d Has a long def 'Imaginary creature that's kind' N(ormal) 'originally' = 1st letter + IS = 'exists'