As concerned about him she was, he may have just gotten that concerned about her. He thought she had seen these plants before, but if she had only seen them in books, would she be alright?
Not wanting to seem like he was doubting her, he chose to not mention any of that. "I'll stay with you, if that's alright," he told her. He kept his eyes alert for the tree that apparently attacked people who got near it, and did his best not to touch anything.