Seedgirls look like ordinary girls but they have a big green bulb on their head. This bulb holds a powder they use to speed and enhance plant growth. My question is how the bulb gets there in the first place.
The bulb could be a part of their body, but that would mean they are essentially humanoid plants, and this would be almost impossible to evolve.
The bulb could be a symbiotic plant, but then why does the bulb rest atop the head. This is still a vulnerable position and the bulb could easily get whacked, sliced, or otherwise hit as the seedgirl walks through her forest home. And, of course, why did the plant develop a symbiotic relationship with the seedgirl in the first place?
The bulb could be a parasitic plant, controlling the humanoid through tendrils that penetrate through the skull, using special spores to expand its neural network (and by extension, its power). However, I really don't like this possibility and it doesn't quite fit with my vision.
So, to restate my problem, these symbiotic bulbs rest atop the heads of their hosts, a race of forest-dwelling women. How did they get there?
To make things even clearer, how would a bulb end up living in harmony with a human atop their head?
The ideal answer will:
Explain what benefits a plant would have for a forest-dwelling woman and vice versa. Perhaps the plant contributes energy and nutrients in exchange for mobility and protection.
Explain how the relationship could have happened. This seems pretty necessary, since nothing quite like this has happened on Earth, unless you count algae and fungi growing in wet sloth fur to be similar.
Explain why the bulb is on the hosts head, despite the drawbacks of being positioned there. Is there any advantages of it being here as opposed to somewhere else. What would be a better place? How would this change the appearance of the Seedgirl?
Attention All Answerers: I have not selected one answer here because I cannot pick just one of these many excellent answers. Everyone, please accept my gratitude and appreciation, as I will be using parts of each answer.