Although the delicate, blowsy peony flower is delicate, the plant itself is not. Yet, with some forethought, they can withstand even the harshest winters without showing any wear.
As a result, they’re a popular choice for gardeners in the northern United States, providing a welcome respite from the bitter cold of winter storms. But how do they deal with such adversity?
Peony plants are frost resistant and will easily survive the winter. They can be grown successfully outside in Hardiness Zones 3-8. Prune them back to ground level each fall and heavily mulch to ensure consistent blooms for decades to come.
How Is Cold Too Cold For Peony?
Neither perennial peonies nor shrubby peonies have any trouble growing in freezing temperatures.
The latter are particularly vulnerable during snowy winters when branches easily snap off at their bases if too much snow accumulates on the shoots.
These majestic trees have wood that is naturally not very elastic and breaks like glass in cold weather.
The plants also don’t branch out well and usually only have a few primary shoots. Because of this, you typically have to put the whole bush on the stick when the damage is there and start over.
But, as with all good things, it’s not that easy. So let’s look at what happens to your Peony when it gets cold.
Plant Hardiness Zones
To find out if your growing region is too cold for peonies, find out what Plant Hardiness Zone you are in.
The Plant Hardiness system, developed by the United States Department of Agriculture, divides the country into regions with similar climates.
It compares average summer temperatures to winter temperatures and allows growers to select plants best suited to their region.
Knowing the region of your area allows you to make informed decisions about how the climate will affect your garden.
Peonies are hardy in USDA Hardiness Zones 3–8. These areas are found throughout the country’s north, particularly inland. Peonies will grow further south, but not well, and will not flower at all.
Do Peonies Get Frost Damage?
Peonies can withstand temperatures as low as -50°F (-45°C), but there is a catch. Only the root can withstand such cold.
The foliage above cannot withstand low temperatures and will wither as the season’s pass. They also perform poorly when repeatedly thawed and refrozen. Their roots require consistent conditions.
This is because Peonies grow from a complex fleshy root known as a rhizome. This rhizome has evolved to withstand extreme temperature changes.
Warm temperatures interfere with the hormonal processes that allow new growth to form, so it’s best to let them freeze. Under deep layers of winter snow, its physical and chemical structures keep it healthy.
What Do You Do With Peonies In The Winter
Prune Peonies to Survive Winter
The first and most important thing to do with your bedded Peonies in the fall is to cut the plant back into the soil.
The foliage will naturally die back over the fall, and once the first frost has finished them off, the entire lot should be removed.
While severe pruning may appear harsh, rotting material attached to the Peony can cause disease problems.
Mildew, molds, and fungal diseases like peony blight thrive on damp, rotting Peony leaves, so remove the wilting foliage. You’ll also need to get rid of it because composting it can cause disease in the rest of your garden.
Avoid pruning before the growing season has finished. The energy gathered in late summer and early fall helps fuel those spectacular spring flowers, so the longer the leaves survive, the better.
Use sharp garden shears (Amazon link) to cut the Peony to about an inch or two above the ground.
The crown, the connective tissue between the leaves, and the rhizome below will be protected by leaving an inch.
Winter Protection With A Rope
A simple protective measure against snow damage is to loosely bind all branches in the upper third of the tree with a non-cutting binding material, like coconut rope, and tie the beginning and end together.
If you want to reduce the surface area, tighten the rope, but not so much that you strain the shrub peony’s branches.
The rope makes sure that all the shoots get the same amount of snow in the winter and that they can all support each other.
Do Not Water or Fertilize
In the late fall, peonies go into a slumber known as dormancy. They slow all metabolic processes above ground and prepare the rhizomes below for a long winter of flower development.
During the winter, you don’t have to apply fertilizer. The Peony has spent the growing season harvesting and storing everything it requires in the rhizome.
At best, it will have no effect, and at worst, you risk chemical burns to the roots and crown, limiting spring growth.
It’s also unlikely that you’ll have to water. They’ll do just fine with what’s left in the soil if you’re at the southern end of their range and to the north. You’ll be too deep in snow to bother with a watering can or hose!
Covering Peonies During Winter
Depending on where you live, a layer of mulch can provide additional protection during the winter months.
While peonies can withstand freezing temperatures, repeated freezing and thawing will knock them around and kill younger plantings.
Heaving occurs when the expansion and melting of new ice beneath the soil forces the roots out of the ground.
A layer of mulch will prevent heaving and protect any exposed roots until the soil thaws enough to rebury them.
Choose a free-draining mulch such as straw, pine needles, or loose bark. This will keep water from collecting around the crown and possibly causing rot.
It will also be much easier to remove loose straw in the spring than a solid soggy mass of compacted material.
However, keep the mulch manageable. The top of the rhizome, or its crown, must be chilled.
If you live in a zone lower than USDA Zone 5, leave the crown exposed over the winter. More than two inches will suffice further north.
Bring Potted Peonies Indoors
Potted peonies are more susceptible to repeated freezing and thawing than soil-grown peonies. Because they lack the insulation of deep beds, bring them in when their leaves turn yellow at the end of the season.
However, you must ensure they receive the same extended period of consistent chill as their outdoor counterparts.
The Peony will not flower unless it is kept below 40°F (4°C) for an extended period. Put your potted Peony in a cold garage, loft, or other dark and sheltered location to ensure it blooms the following year.
You can also cut it back to the soil like a bedded Peony. Only water them when the soil is arid.
When spring arrives, you can replant the Peonies in their usual location and let the magic of warmer temperatures and longer days bring them back to life.
Avoid Repotting During Winter
Avoid disturbing a Peony rhizome during dormancy by not repotting indoor Peonies during the winter.
It may appear to be the easiest time to do it because there is no foliage in the way, but you risk damaging the roots and preventing new growth in the spring.
Also, they may appear to be sleeping, but that rhizome has a lot of activity!
The best time to repot or transplant Peonies is in the late fall, just after they die. After that, they are not completely dormant, and the spring’s new growth has yet to emerge, so there is less risk of damaging buds.
Preventing Frost Damage in Tree Peonies
In contrast to their more common shrub-like herbaceous cousins, tree peonies do not entirely die back to the ground every fall.
Instead, they shed their leaves while leaving most of the plant intact. As a result, they do not require the same amount of pruning to survive the winter.
They, too, are frost-resistant but benefit from some protection. Planting them with some wind protection is a good start.
Mulching heavily will protect the roots and keep the temperature stable. Allow an inch or so of clearance around the trunk to prevent moisture from accumulating and causing rot.
If you live near the top of the Peony’s range, you can protect the tree by wrapping it in burlap.
Smaller specimens can be covered entirely, while larger specimens can be wrapped in strips around their branches and trunk. Remove the wrappings once the spring thaw begins.
Do Peonies Come Back After Winter?
Year after year, peonies are renowned for regenerating from almost nothing to a thriving shrubs exploding with massive, fragrant blooms.
It’s nothing for them to repeat this cycle of death, sleep, and rebirth year after year, if not centuries. They are great plants that will not be slowed down by the chill of winter.
You can resume watering and fertilizing your Peony once the emerging shoots reach 12 inches (30cm) tall. Avoid getting fertilizer on the crown, as this can result in burns.
Applying it 6-12 inches away from new growth is best. You can also fertilize them once they begin to flower. Slow-release granules (Amazon link) work best for potted peonies.
Finally, remove excess mulch, so the crown is only covered by an inch or two of soil. If they push through too much soil, the Peony will expend energy that could be spent on flowers instead.