Jade Fern Grove damage control

Bazi rather enjoyed the temper-tantrum that followed, imagining Swift's rage as a beam of hot light going straight through his father's stupid head. It wasn't until her son suddenly started spouting medical facts that her internal grin faltered, replaced by a knotting sensation in her gut. Bazi padded forward and around her child's slumped body, lowering her head and seeking his eye. "Swift," she began, studying him  as she might a stranger. "How do you know about yarrow?" Bazi had almost forgotten the word - and the plant, even though it was the only natural remedy she had ever been introduced to. No-one else had come forward as being even remotely interested in the art of such things, so then, who had taught Swift?