Sorry for the vague title, I want to know about two things concerning this item in Dark Souls 2.
After the first invasion, is this item guaranteed to spawn? Generally the wiki states that this is a 10% chance top spawn after each invasion. However this seems off because after the very first player invasion in a new game, this item is always there. However after that, the 10% seems to kick in.
Do NPC Invasions count? Again, the wiki is vague on this topic and just states:
It has a 10% chance to grow on the corpse again after each time you're invaded.
Best Answer
Yes. The seed will be spawned by NPC's.
It has been confirmed that NPC red phantoms will cause the Seed to spawn at the same rate as regular invasions. Note that Grey Phantom and RSS invasions DO NOT count towards getting the Seed.
I'm not sure if this same concept applies to the different types of player invaders, but it may be worth looking into. It is a guaranteed drop previous to the invasions like you pointed out in your question.