Peonies are a classic, old-fashioned flower in northern gardens with a long history in Minnesota. Brand Farms in Faribault had acres of peonies under cultivation in the 1920s, earning the town the nickname the "Peony Capital of the World." There are still several big peony growers in Minnesota, including Swenson Gardens in Howard Lake, Mn., and Hidden Springs Flower Farm in Spring Grove. Once established peonies are an easy-care perennial and, in the right conditions, put on an annual show of blooms that is spectacular.
There are three basic types of peonies: herbaceous peonies come up each spring and die to the ground in the fall; tree peonies are shrublike in appearance, with a beautifully shaped leaf, and grow from woody stems each year--you do not want to cut these back in the fall; Itoh or intersectional peonies are a combination of the two traditional varieties--they have the same pretty leaf as tree peonies but die to the ground each year.
Siting and Planting
Peonies like plenty of sun and well-drained soil, so choose one of your sunniest spots in the garden. They will grow in partial shade, but the number of blooms will be smaller and the plants will never achieve as much vigor as they have in the sun. Also, give peonies adequate space so there is good air circulation around them. Peonies can last for decades, so put your plants where they will be happy.
Peonies are usually sold as bare-root plants to be planted in the fall. The roots take their nutrition from below, so prepare a large hole with plenty of organic matter. They also like good drainage, so you may want to lighten the soil around them with peat moss. The root usually includes a thick piece in the middle, with smaller roots coming off it and eyes on top. (Here's a good illustration.) Plant with the eyes 2 inches below the surface of the soil with the eyes point upward. Fill in around the plant, water it deeply and wait until spring.
Care and Maintenance
Like most perennials, you will need to make sure the peony is well watered in the first year -- an inch or so a week from either Mother Nature or the hose. Water at ground level to reduce fungal diseases. If you get flower buds the first year, remove all but one or two. You want the plant to put its energy into forming strong roots.
After bloom time, add a bit of fertilizer around the plant. You could also add bone meal in the fall. Peonies do not need a lot of fertilizing. When herbaceous peonies die back in fall, clean up the foliage to reduce the chance of a disease. Care for tree and Itoh peonies is similar, but you do not cut back tree peonies.
That's about it: Sun, well-drained soil, a bit of fertilizer, good air circulation.
Once established, peonies will bloom for years to come, providing a sure sign of summer each June.