Class and Level Geekery XVIII - Everyone's an Expert

[Metastachydium]

So...was this a graft in the conventionally-horticultural sense as well?

Absolutely! Especially given that quite evidently, trolls are basically planties (just think about it: they are green, they can regrow lost parts of their body and fire does nasty things with them) that are able to ennoble clearly inferior non-plant organisms by making them part plant.

Would that make Serini technically a child of the donator troll?

"Parasitic twin of the donor's actual offspring" might be more accurate, but yes, you could say that.