Peonies can live and thrive for decades, with minimal care. Peonies bloom in the late spring, but 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.
How to Plant Peonies
What to Plant: Peonies can be transplanted as plants, but just as often you’ll be planting the tuberous roots. Either way, the peony root should contain at least 3 eyes. Peony eyes are small reddish buds, similar to the eyes of potatoes, that will eventually become stems.
The reason for the rule of thumb of 3 eyes on each transplant is so that the tuber is large and strong enough 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 flower.
Plant with the eyes facing upwards and the roots spread out.
Soil: 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.
Depth: 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.
TIP: Be sure you don’t start accidentally burying your peonies deeper when you add mulch to your garden. Keep the mulch away from the base of your peony plants.
Space: Give each peony plant enough space to grow to maturity without being crowded. That means about a 3-4' diameter for each plant. Peonies are especially prone to gray mold (botrytis) when planted too closely and denied air flow between plants.
Site: 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.
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 divisions. 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.