Peonies can live and thrive for decades. And bees love them!
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 straightforward. 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.
When to Plant:
Peony growers dig their peonies in the fall and this is definitely the best time of year to plant them in your garden!
A peony planted in the early fall will have the opportunity to put out a good number of feeder roots before the following spring. I’ve noticed in my garden that fall planted divisions that have had several weeks of growing time before the ground freezes, do better the following year than those that have had less time to develop new roots. This is particularly important if the spring is hot and dry.
Peonies can however be planted right up until the ground freezes if necessary.
A word on spring planting….peonies purchased in the spring more than likely have been held over winter in cold chambers. Planting them in the spring without letting them have the benefit of fall feeder root growth puts the plants under severe stress. Peonies being the tough plants they are will usually recover, however they have suffered a set back and will likely not establish as quickly as those planted in the fall.
A few garden centres will pot up peonies in the fall for sale the following spring. Though containers are not ideal growing environments for the bulky roots of peonies, at least they have had the opportunity to put out some feeder roots in the fall. This is not the case for those peonies potted up in late winter or early spring.
If you are buying peonies from a garden centre, ask a) what size of plant is in the container i.e. a 2-3 eye or a 3-5 eye division for herbaceous and Itoh peonies and 1, 2, 3 or 4 year old plant in the case of a tree peony and b) when was it planted i.e. last fall or recently. Plant containerized plants as soon as you can get them into the ground.
Cooperate with nature and plant peonies in the fall!
Where to Plant:
Herbaceous and Itoh peonies generally prefer cooler climates and are easily grown from USDA Hardiness zone 3 through 8. Gardeners in zone 2 and 9 however have reported success with some peonies.
In general, herbaceous and intersectional peonies require a sunny, well drained location. They will however accept, and perhaps benefit, from some light shade in areas that have very hot dry summers. The rule of thumb is that 6 hours of direct sunlight a day will ensure maximum flower production.
Tree peonies have a slightly different growing range. They can be grown in USDA Hardiness Zones 4 through 8 or 9 but require winter protection in Zones 4 and 5 to bloom reliably. Tree peonies will also support more shade. Deep shade however will reduce flower production. The best shade is that provided by a high, light foliage canopy.
Standing water is the number one enemy of a peony!
If water is allowed to stand on the crown or around the roots, rot quickly sets in and the plant declines and can actually die. Peonies, like roses, are heavy feeders and enjoy a heavy fertile soil. They do well in heavy soils however the trick is to ensure that drainage is impeccable.
How to Plant:
Peonies are heavy feeders and do not appreciate being moved so it is important to ensure they are planted in good, fertile soil. If the soil needs to be amended it is best to use compost or very well rotted manure. Fresh manure is reputed to burn the plant and spread pathogens.
If you are opening up a new area for planting consider having soil tested for pH and nutrient levels before planting. I believe peonies prefer a pH of between neutral and slightly acidic (pH 6.0 to 7.0) but they seem to tolerate a wide variation. The soil testing facility will usually make recommendations as to fertilizer requirements to correct any imbalances. Though soil testing is not a necessity, it can be useful to know your exact growing conditions, not just for peonies, but for all your plants.
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.
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.
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.
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.
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 fewer 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.