The Whomping Willow is a female tree, that seemed odd since usually plants had both sexes of lowers growing on them so the can reproduce and grow, didn't the professor know that, guess not but that does not suprise me.

Fred sighed and approached the willow and said sweetly, "You're a beatiful tree, here a gift so you you can keep growing strong", Fred said and then spread the moon calf dung along the dirt near the tree's roots and then slowly backed away to give the next person the chance.