Amorphophallus slow into growth this year.

I have a number of Amorphophallus that I overwinter in a cold greenhouse in dry compost. In the past few years, by now, I've had flowers and the foliage is through and unfurling. I've just been out in the greenhouse checking these and they are only just starting to shoot and the largest tuber has only the barest signs of growth starting. Dahlias and fuchsias overwintered alongside are generally on schedule.
I was wondering whether other people have noticed this sort of thing. Or have any idea what may have caused this slow start. It doesn't appear to have been significantly cooler this spring and I did see that April was the sunniest since 1942.

 

I think that the whole of this spring has been cold. More sun maybe but still cold, especially at night.

I have Amorphophallus albispathus and I rarely see any growth until at least the end of May. This year is no different.

 

One of those things I guess.
A lot of my Hostas were slow to get going this spring.

What species of Am do you have?
I had quite a few (even sourced some of the tropical species) at one point.

 

Currently only got konjac and bulbifer. I had stipitatus but lost it a couple of years ago.