It's too bad to see a fresh flower on a heap of cow-dung. He'll be the ruin of her!
《新英汉大辞典》
2
她人品很好而他脾气差,简直是一朵鲜花插在牛粪上。
She is very nice and he is bad tempered. They are a match of beauty and the beast.
3
坦诚地说,她的父亲不喜欢我,认为我跟他的女儿在一起是“一朵鲜花插在牛粪上”。
To put it bluntly, her father doesn't like me and the thoughts of his daughter getting jiggy with me is like putting a pretty flower on a piece of dog poo.