He doesn't react all that much when Frisk wakes up, beyond a slight raising of one eyebrow; after a moment, he just nods slightly. "Yeah."

It's not until he's stood up and is in the process of shouldering his pack again that he tilts his head toward the bed of flowers. "Does that happen every time?"

He doesn't specify how the flowers got there, of course. He's got no idea if Frisk knows, but he kind of doubts it.