I have a packet of seeds. It says on the packet "often germinates in
spring".

In Peter Thompson's "Creative Propagation" it says Astrantia is one of
the plants whose seeds benefit from heat conditioning and in the table
at the back it says to plant conditioned seed in August or September (or
that is how I interpret the entry "8/9" in the "Seeds Cnd" column).

I am considering dividing the packet into 4 and sewing one quarter
outside and another inside next month and then the same again next
April. Any advice?

We have some Astrantia Major which we bought as plantlets locally, it
has thrived and continues to spread. We have been on the look out for
some Maxima for a while but not come across any, hence the seeds which
come from Plant World Seeds.

--
Ellis Morgan