I can answer that for you! I used to work for the wildlife service here in TN. All of the bugs that pollinate the daylilies- bees, moths, butterflies, etc attract the frogs and they end up using the flower as a good shelter/ hunting hole!
TomThumb - to the Daylily Forum! And yes! I do believe that might be the biggest reason they hide in flowers and other places! Tree Frog DO have to keep a level of moisture in their bodies or they dry up and die. Thanks for pointing that out!