The Hazards of Love 1 (The Prettiest Whistles Won't Wrestle the Thistles Undone) Lyrics

Lyric discussion by mister care-too-much 

'The prettiest whistles won't wrestle the thistles undone' ^ Huh? Is that a sort of 'childhood can't be regained' theme there? Thistles, if I'm not mistaken, are a type of thorny flower. It is implied that they were caught somewhere (since they can't be 'wrestled undone'), which could in turn imply a sort of violation/ending of childhood. What is this people are saying about a rape? Also, whistles are reminiscent of childhood toys...so something as insignificant as a toy, no matter how pleasing the sounds it makes, can't revive a lost childhood? Is that what Colin's getting at?

Also...shouldn't it be 'lissome' instead of 'lithesome'? Lithesome is pronounced with a long i sound, and he says it with a short i. Lissome and lithesome mean the same thing.