Big and ruffly, fragrant and elegant, peonies have been a favorite perennial flower for more than a century. Swenson Gardens owner Becky Swenson says, “There’s a lot of emotion connected to peonies.” And she should know! Her company has 15,000 peony plants and about 250 varieties, which makes them the world’s largest hybridizer of new peony varieties.
Peonies grow in most U.S. states, including Alaska, with varieties that can handle USDA Plant Hardiness Zones 2 through 8. “When you’re in a cold climate, you’re eager for color,” Swenson adds. “The blooms are so beautiful.”
Where to Plant Peonies
Make sure you don’t plant peonies where they’ll compete with nearby shrubs or trees for light and nutrients. Plant in good soil where they’ll get at least six hours of sun; eight hours is ideal. For growers in the southern Plant Hardiness zones, peonies may need some cooling afternoon shade.
If you’re limited to a patio or balcony, plant peonies in a container. Look for dwarf varieties, and make sure your pot is at least 18 inches deep and wide. Potted peonies need ample space for the roots and multiple drainage holes to prevent rot from over watering or excessive rain. They will also be more susceptible to freezing temperatures and may need to be stored in a sheltered garage over winter.
When to Plant Peonies
Most growers ship bare-root peonies in the fall, which is the ideal time to plant them and get them acclimated by the next growing season.
Swenson advises buying from nurseries in your growing zone so the peonies are already acclimated.
In the spring, you can find potted peonies at garden centers. If they don’t bloom the second year after planting, it may be because they’re storing up energy depleted by the transplant and first-season blooms.
How to Plant Peonies
Dig a hole about twice the width and depth of the root you are planting.
Mix some of that soil with composted cow manure and a cup of Milorganite and return it to the hole.
Place the roots with the eyes (the little red buds you’ll see emerging from the top of the roots) facing up. They should not be planted deeper than one or two inches from the covering soil.
Itoh (also known as intersectional) peonies should be about two inches deeper than common varieties.
How to Grow Peonies
If you have healthy soil that’s been amended with compost, you shouldn’t need additional fertilizer.
Don’t over water. Peonies need thorough watering when first planted, but they don’t like to be soggy and subjected to the constant spray from an automatic sprinkler system. Unless you’re in a sandy or dry area of the country, established peonies shouldn’t need supplemental watering.
Peonies also don’t like to be crowded; they need space and air flow. If that’s a problem, relocate your peony or divide it into small plants.
How to Divide Peonies
The easiest way to relocate, share or swap peonies is to divide them in the fall, usually between late August and late October.
Dig up a section of your peony plant with a sharp spade to isolate it from the portion you are leaving in the ground. You can also dig up the entire plant if that is easier.
Gently knock off loose soil around the roots.
Use your hands or the spade to separate the plant into smaller sections with three to six eyes each.
If your peony is thriving and doesn’t need to be divided, let it be.
How to Support Flopping Peonies
With large flowers and soft stems, common peonies can flop over when in full bloom, especially when a spring rain adds weight to their top-heavy blossoms. You can help keep them upright in several ways. Low fencing for a border of peonies can help, as well as metal plant supports you can push gently into the soil while the plants are still emerging.
Itoh peonies have sturdy stems and don’t need staking.
How to Prepare Peonies for Winter
Cut peony stems to the ground and cover them with mulch to insulate against weather and temperature extremes in early and late winter. An early warm spell might trick your plant into blooming too early and then getting hit with a freeze. Loosen and lighten mulch when the danger of spring frost is gone.
When Will Peonies Bloom?
Most peonies bloom for a week within a four- to six-week stretch from late May into June. To keep the colors going, plant a mix of early-, mid- and late-spring bloomers.
Do Ants Hurt or Help Peonies?
You may see ants taking advantage of the sugary nectar on peony buds and blossoms. Ants are most attracted to the old-fashioned varieties with the sweetest smell.
Ants don’t harm the flowers. But they also don’t help unfurl the blossoms as some people believe.
If you’re bringing in fresh-cut blooms, give them a gentle shake or swish them in a bowl or bucket of water to dislodge ants from the flowers.
Do I Need to Cut Off Spent Blooms?
Yes. Once blooms start to wilt and lose petals, cut them off with sharp scissors or a pruner. You can clip them right below the bud or go down as far as the first leaf joint. This keeps the plant from putting its energy into creating seeds and saves it for next year’s bloom.
Are There Peony Diseases to Watch For?
Peonies that are too crowded or wet can be susceptible to soil- or airborne botrytis (a fungus). If you see black spots or mildew on peony leaves, remove those stems and put them in the garbage, not your compost. You can treat the plant with a fungicide. As an alternative, Swenson Gardens suggests skipping the chemicals and moving the peony to a new location with uninfected soil.
Where Can I Find More Peony Advice?
The American Peony Society has a wealth of information online, including a listing of national and international public peony gardens. You can also find regional groups of peony growers for local resources and growing advice.