Peony plants can live, bloom, and thrive for decades, with minimal care. Although peonies bloom in the late spring, they do best when planted or transplanted in the fall. For the most part, planting peonies is pretty straight forward. However there are a few special needs peonies have, that are best accommodated at planting time. In particular, the choice of where to plant peonies and how deep to plant them.
Where to Plant Peonies
Peonies need at least 6 hours of sun each day and a full day of sun is even better. Without sufficient sunlight, you’re going to get less blooms and smaller flowers. Plus, your plants stand an even greater chance of getting a fungus disease, like gray mold.
Preparing the Soil of Planting Peonies
Peonies are very adaptable, but ideally they like a well-drained, slightly acidic soil(6.5 to 7.0 pH).
If you are planting in heavy, clay soil, amending with compost or a soil mix labeled for azaleas and rhododendrons, before planting, will make it easier for your peony plant to settle in. Since peonies can remain in the same spot for upwards of 70 years, taking the time to prepare the soil before planting is time well spent.
What Part of the Peony to Plant
Peonies can be transplanted as plants, but more often than not, you’ll be planting the tuberous roots. Either way, the peony root should contain at least 3 eyes. Peony eyes start off as small reddish buds, similar to the eyes of potatoes. They eventually elongate and become stems. In the photo, you can see the start of these white stems.
The reason for the rule of thumb of having at least 3 eyes on each transplant is so that the tuber is large and strong enough when planted, to survive and bloom within a couple of years. A root with only 1 or 2 eyes will still grow, but it will take longer to mature enough to set flowers. However don't toss out a tuber just because it's small. It's still worth planting, but you will have to be patient.
How Deeply to Plant Peonies
Peonies like a good chill in the winter. In order to set their flower buds, peony roots should be planted relatively close to the soil surface; only about 2-3 inches deep. It may feel odd to leave roots so exposed, but peonies actually need this chilling to attain dormancy and set buds.
Dig a hole large enough to spread the roots out. Mound the soil in the center of the hole and spread the roots out and over it.
Make sure you plant the tuber with the eyes facing upwards. You don't want the plant to expend all its stored energy turning the stems around to grow upward.
How Much Space Do Peony Plants Need?
Give each peony plant enough space to grow to maturity without being crowded. That means about a 3-4 ft. diameter for each plant. Peonies are especially prone to gray mold (botrytis) when planted too closely and air is not allowed to flow freely between plants.
You shouldn’t need to divide your peonies for many years. In fact, peonies dislike being disturbed and often don’t bloom for 2 or 3 years after division. However, if your peonies are growing in good conditions and they still aren’t flowering well, it could mean that it’s time to lift and divide them. Use a sharp tool to divide the roots into sections with 3-5 eyes each and replant ASAP. Follow the same steps for transplanting as for planting.