Peonies have become not only a trendy perennial, but one of my favourites to use for both flower colour and foliage in the garden. They are technically deer resistant. Though we know that when deer are hungry enough they will eat anything and everything. If you choose the right site and they are planted correctly, you can minimize and avoid any powdery mildew that plague some gardeners with their peonies.
Peonies are a plant that can be staggered in the flower border. Depending on the variety, they can add 30-36" height. Some new varieties are called Patio Peonies and can be successfully grown either in a container or at the front of the border without flopping over.
Peonies do not need to be a high maintenance plant. Avoid planting with soil up against their stems. As well avoid the placement of mulch directly against the plants stalks. When peonies become mature, you may find that they also become floppy. This can definitely be a drag. You have some options. There are metal hoops that can be placed over peonies in early spring to ensure some support as the plant grows. Best done before your peony needs the support as you dont want to bend or break the stems as you force your peony into the supports. Some gardeners prefer natural supports. Using branches from your garden you can artistically support your peony stems. As well, you can try planting other plants close by that might allow for some support given by them. They could include Hydrangeas , dogwood, burning bush. These would be somewhat woody plants that have natural support.
What I do to overcome floppy peonies in my garden is to harvest the flowers and give the plants a light shear to help them keep their shape and show off their foliage for the rest of the year. I also keep my peony clumps on the smaller size. Dividing them every three to five years ensures that I have more plants, less powdery mildew because ive improved the air circulation and increased the vigor of the plants by reducing the size of the plant.
I also have switched from a garden variety of a peony to a "Itoh" peony. Yes, it is initially more costly than a regular peony. BUT, it produces larger flowers and does not require staking, dividing or succomb to powdery mildew. The plants themselves are larger as this peony is a cross from the loved tree peony variety. The leaves are stems are more upright in habit. My favourite!! Whenever mother's day comes around, I ask for another. And you should too! Right now I have 4 Bartzella's in my garden. They are double yellow. Stunning!