When does a peony give its flower?

Peonies are planted in autumn and bring their beautiful flower in spring in most climates in the months of May and June.

Peony flower blossoms come in four different shapes. A single shaped blossom has only a single layer of petals around the center. A semi-double has two, maybe three layers of petals around the cent. A double has a crowd of petals so that the center is not visible. A Japanese looks much like a semi-double but instead of the typical stamens in the center, the center is filled with tiny petals or petaloids.

Peony flowers are large and colorful. Peony flowers range in shape and style as well as color. Many peony flowers are extremely heavy, and the plant should be given proper support in order to bear the weight of the large bloom. Of all the flowers you can grow, peonies are often the most luxurious and spectacular blooms in an early summer garden. Peony flowers are also a favorite of artists in almost every culture. Peony colors range from white, cream, and ivory through myriad pinks, roses, yellow, lavender and dark reds.

What depends the size of a peony flower?       What is a peony?