In message .com,
TomKan writes
Do they bloom more than once?

Yes. But not reliably. It depends on your conditions.
Are the seed pods capable of being planted? If so, when should they be
harvested and how do you keep them until the next year?

It'd make more sense to sow the individual mericarps (which are usually
treated as seeds) or even to extract the seeds from the mericarps. The
mericarps can be collected when the fruits have dried out on the plant,
and may be stored by keeping them cool and dry (e.g. in a sealed
contained in a refrigerator - not a freezer).

Will the seeds from a black bloom hollyhock produce black bloom plants?

Some of the time. (I bought a supposed black hollyhock this spring, and
the first flower has opened pastel pink with a soft yellow centre.) If
you grow black hollyhocks distant from other hollyhocks I'd guess that
they'd come reasonably true to seed - there's plenty of strains of black
hollyhock seed on the market. If you grow them near other hollyhocks (of
the same species) then it's likely to be a case of pot luck.
--
Stewart Robert Hinsley
http://www.malvaceae.info