What if the secret society that Quirin was/is a part of was a secret-service type bodyguard force to the King?
Then it wouldn’t be very secret, would it?
Frederic called Quirin, “my old friend.” They’ve know each other a long time, possibly back before Frederic was the king.
But, ooh! New theory that just struck me! What if Frederic and Quirin and their secret society knew about the flower from a long time ago? They didn’t know where it was, but they believed it existed. Maybe it’s Frederic who ordered the people to search for the flower to save Arianna, because he knew it was out there somewhere, and that was his last hope. Maybe he knew pulling the flower up would eventually result in the spikes, but was willing to risk it to save her and their unborn child!