Many flowers are said to be thus, but I would go with ROSE.
..."The rose is considered the most beautiful flower in the world, which is why it's called the “queen of the garden.” It's one of the most popular flowers worldwide, and it comes in different sizes and colors. .."
But lots of people have said the same with other flowers, so it really does depend what your quizmaster wants.
A young beautiful girl is often described as a rose.