When do I harvest the seeds from a seedpod?
Are hydechium self-fertile or do they need to be cross pollinated?
Here is a link that might be useful:
Hedychium seedpods will pop open when ripe. The inside of the pod is usually orange and the seeds covered with red pulp (see 2nd photo from top on the link). You can generally see 3 fissures forming along the sides when they're just about ready to pop, and could harvest them then, but if you wait until they open up you'll get most of them, as they don't scatter that much until they dry out a bit. Even if they fall on the ground they're pretty easy to see and retrieve when still fresh.
Some will self-pollinate. I don't know if they all will, but some varieties seem to set seed much more readily than others.
Here is a link that might be useful: Seed pods