I've stopped grow or should I say trying to grow the Calla Lily for this reason
plenty of foliage and no flowers I've tried for about 6 years now bought with a good show of flowers but always fail to flower the following years I really think it's down to the climate we have in the UK Thomas you are not alone if you search calla lily in the search box above you will find lots and lots of old posts regarding this lily
I moved on to Hosta's as one year all my pots containing the Lily had turned to mush I even when to my GC for advice and all they said is are you feeding it.
Hopefully an expert on this Lilly will come along with the answers you need but for me I’ve spent to much money on this Lily and failed to try again.
Here are some external links