The blood thirsty wild weed

Prince, oh prince atop your white stallion steed
holding in your hand a quite wild weed
let me tell you prince that the weed will transform
it will show it's true self and become a lovely rose covered in thorns
but be warned the thorns will prick
be warned that your sweet red blood will drip
you have been deceived, so i warn you prince to drop the weed and leave it in the dirt to grieve