Posted: 27/07/2016 at 12:40
I've never heard of C. grandiflora and google finds few references to a red list plant in the Ulkraine.
Are you sure it's not C. cordifolia or maritima?
Both of these die right back in winter. I had several non-flowering years with C. cordifolia and eventually dumped it. Or thought I'd dumped it, I can see the leaves peeping out between some alliums now.