Hi Fabrizio,
Here is what i think :
let's start from this labelled A. bulbifer (from pictures on internet does not seems the right one), this bulb has grow a lot in 2 years:
a detail from leaves it is quite peculiar and different from other Amorphophallus:
Looks like Sauromatum venosum
this is a small bulbifer but the leaf is very similar to the big one:
The bulb looks like Sauromatum venosum, but the leaf looks like another species, maybe a Typhonium species?
typhonium venosum indian giant
Again, the bulb looks like Sauromatum venosum, but the leaf looks like another species, maybe a Typhonium species? Is the picture of the leaf from the bulb in the first picture?
2 Amorphophallus paeonifolius already digged out took a picture of the bulbs just out of the pot
first:
This is Amorphophallus konjac
second:
This is Amorphophallus konjac
Amorphophallus paeonifolius still green leaf is different from others
This could be Amorphophallus paeoniifolius
this year I have sown Amorphophallus titanum (hope this is not mislabelled)
It is just putting a second leaf what do you suggest? do I have to try to extend growing period or not?
This looks like Amorphophallus titanum. When seeding Amorphophallus the second leaf can come when the first leaf is still there.
Those are some bulbe that a friend of mine from Puglia gave me he digged it out during a work in his olive trees:
Arum species, but impossible to tell which one without close-up of the male/female flower parts
Best regards,
Maarten