I don't have that variety, but mine seem to do best with fresh seed.

There's a page on these on aroid.org. I've put the link below.

George

Here is a link that might be useful: Arisaema seed

Thanks for the responses. The link is very helpful.

Candidissimum gives so many offsets (at least for me) you will probably find it simpler/quicker to propagate from those rather than wait for seed. Mine flower second year from offset.