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Chilling Peonies: What Are Peony Chill Hours

Chilling Peonies: What Are Peony Chill Hours


By: Tonya Barnett, (Author of FRESHCUTKY)

Peonies are a classic landscape plant. Frequently found near old farmhouses, established peony bushes can return for decades. With colors ranging from white to deep pink-red, it is easy to see why peony plants remain a popular choice. Though the plants are generally easy to grow, there will be considerations when deciding to plant peony bushes.

Most important among these is the need for proper climate, include chilling. Choosing the correct variety and growing location will be key in establishing a thriving peony planting.

Peony Chill Hours

Peony plants grow best in regions with periods of cold weather during the winter months. Before planting peonies, examine the specifics of your growing zone and determine whether or not it is suitable. Most peonies will grow well in USDA growing zones 3 through 8 where they will receive the required amount of “chill hours.”

Simply, chill hours refer to the amount of time that the plants are exposed to cooler temperatures throughout the winter, most often between 32 degrees F. (0 C.) and 40 degrees F. (4 C.). These hours accumulate until spring arrives and may differ greatly from one region to another. Without proper chilling, peonies will fail to set blooms.

How Much Cold Do Peonies Need?

With this information in mind, you may ask, “How much cold do peonies need?” Peony chill hours can vary from one variety to the next. However, most chill requirements for peonies are around 500-1,000 hours.

The number of chill hours in your region can easily be found through the use of online weather calculators. While many northern growers will have no trouble chilling peonies, those living in warmer regions may need to consider choosing varieties that only require low chill hours.

Chilling Peonies

While chilling peonies is best accomplished in the ground, these plants can also be grown in containers. When grown this way, chilling requirements for peonies will still need to be met, but can be done by storing the potted plants in a minimally heated space which does not freeze.

Chilling is imperative in ensuring the growth of healthy, vibrant plants the following growing season.

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Peony Care After Blooming: Discover the Best Way to Get More Flowers

What you do for your peony care, after blooming, determines the quality and quantity of next year’s flower show. Something to remember with peonies is that much of what you do this year is to encourage blooms next year. And there is a lot you can be doing.

Without the proper care and attention, your peony can be left directing energy into seeding new plants, when all you really want to do is get it producing more flowers. In that respect, peonies need a little garden training.


How to Grow Tree Peony

Tree peonies sold nurseries and garden centers are typically the result of grafting. The scion is a tree-peony cutting that has been grafted onto an herbaceous rootstock. Be sure to plant the graft union at least 2 inches below the soil surface. Some nurseries recommend more follow the instructions on the label, if any, that come with the plant. Often, there is a plastic ribbon indicating the recommended planting depth. Proper depth will promote the establishment of the scion's root system.

Like the herbaceous peony flowers, tree peonies do not like to be transplanted. So find a suitable home in which to establish them when planting, and consider it their permanent home. Tree peonies are very slow-growers and may take three years before new plants fully establish and begin to flower. Once established, they are long-lived and need little maintenance.


Passion for Peonies! How to Plant, Grow and Care for Peonies in Your Garden!

How to Plant, Grow and Care for Peonies

Herbaceous peonies are handsome perennial shrubs that produce extraordinary, romantic blooms, many with exquisite fragrance, that thrive and bloom for 100+ years with little care. The key to growing spectacular peonies is getting them planted correctly . From that point on, little care is required for stunning blooms year after year.

When you plant a peony, you are participating in history. Your plant will grow and bloom for 100 years or more with little care. In the decades when people struggled to recover from the devastation of the American civil war, peonies were found blooming merrily in deserted, war torn fields, where nothing remained of the homesteads but the soot stained foundations. Blooming peonies gave hope that life persisted and beauty would come again.

Peonies are cherished for their enormous, romantic blooms. Though the blooming for any given peony shrub lasts just 1-2 weeks each spring, you can extend the blooming season of peonies in your garden by planting varieties that flower at different times within the peony blooming window. Let's see how to get your peonies off to a perfect start!

How to Plant Peonies

What Climate for Growing Peonies

Before planting a peony, first determine if your climate is suitable for growing peonies. These are long-lived perennial shrubs that need a seriously cold winter in order to bloom. While some gardeners in more mild climates have had some success sometimes, a general rule of thumb is that peonies need thirty consecutive days below freezing to reliably bloom for you. All garden peonies thrive in climate zones 3-7. For gardeners in zone 8, select the early blooming peonies for best results, as this gives your plant time to fully bloom before the high heat of summer sets in.

I know how much gardeners in Southern California and Florida long to grow peonies. Don't break your heart over a plant that needs a climate so different from your own. Insufficient winter chill is one of the two causes for peonies not to bloom .

When to Plant Peonies

Peonies can be successfully planted in the fall or the spring, but it becomes well established most easily when planted in the fall. Be sure to pant six weeks prior to the first hard ground freeze.

Select the Site to Plant Your Peony

Remember that planting a peony is a long term investment in your garden's beauty, so take care when you select the site where you want to plant it. Peonies are genetically geared for the long haul - since they grow and bloom for a hundred years or more, they take a far reaching view of life. Do not expect blooms the first spring after planting. One or two might surprise you! For the first few seasons, the bloom production is very small, but building. From year three on, look for bushes loaded with blooms!

Peonies do not like having their roots disturbed. This is why the bloom production is so scanty when first planted. If you were to take a flourishing peony that reliably blooms heavily every year, dig it up and replant it just 3 yards away, the bloom production will crash, and it would be nearly as long to full bloom as if you had just planted it for the first time. So be sure you want it growing where you plant it!

Sun Exposure for Peonies

Plant your peony where it will get direct sun for eight or more hours a day. In climates with a very hot summer, plant for morning and afternoon sun, but provide a bit of light shade during the heat of the day.

Preparing Your Soil for Peonies

Peonies will thrive in a wide range of soils. To prepare your soil for planting your peony - dig a hole 12-18" deep, breaking up compacted soil, and amending heavy clay with compost, dried grass clippings and dead leaves. Incorporate amendments as needed to ensure good drainage, and add about a cup of bone meal, well mixed into the soil at the bottom of the hole.

Identify the Eyes of Your Peony

Examine your bare root peony, looking for the "eyes". Like the eyes on a potato, these are the points where new growth will develop. Often, (but not always), the eyes on a peony are a bright pink swelling. Take note of the side with the most eyes - you want that side facing up when you plant it.

Planting Depth for Peonies

The two most important requirements for peonies to bloom freely are a climate with sufficient winter chill and the correct planting depth!

Form a large cone of soil in the hole you dug, firming it down to eliminate air pockets as you go, with the top of the cone of soil rising almost to the level of the ground. Place the bare root peony on top of the cone, with its roots draping down. Position it with the side with the most eyes facing up. Back fill with loose soil, covering your peony root with no more than ½ - 1 ½ inches deep . This shallow depth is critical. Planted deeper, your peony plant will still grow healthy and strong, but with few or no blooms. Planting peony roots too deep is the single greatest cause for impaired blooming where the climate is sufficiently cold in winter.

Level the soil with the surrounding ground, tamp it down firmly and re-check the depth of your peony root. If it is deeper than 1 ½ inches, adjust it to the proper depth and water well. Once the water has been fully absorbed, again re-check the depth of the peony root to be certain is has not settled further below the surface of the soil.

Congratulations!Your peony is now planted perfectly! :)

Peony Care

Now that your peony is planted perfectly, let's review the care you should provide.

Support Your Peonies

The large peony blooms will catch and hold rain, becoming so heavy that the stems can no longer hold them upright. This is particularly an issue for the "bomb" flower form varieties. It is a terrible disappointment to find your peony flowers finally open - only to have fallen face first into the mud. Add a ring style support when you first plant your peony, or in the early spring when new growth is first sprouting. New growth will grow up through the lattice, fully supported and obscuring the ring.

Watering Peonies

Provide moderate moisture for your peony plant. Understand that fewer, deeper waterings is best, as this will promote large, healthy roots.

Feeding Peonies

For best results, provide a yearly application of an all-purpose fertilizer with a top dressing of compost. Do not mulch your peony - the plant will respond as if it is planted too deeply.

Pruning Peonies

While strictly speaking, peonies do not need pruning, c utting them back in late fall prevents any insect damage or disease from overwintering in the plant and gives the garden a tidy appearance. W here two branches cross and rub against each other, select the lesser branch to be pruned right back to the base. That point of friction causes a weakness where insects or pathogens can move in.

Ants on Peonies

Just this morning, a customer said "I love growing peonies, but I just hate the ants!" This is a common complaint among gardeners. But I want to speak up for the ants, who are performing a crucial service for the peony, in exchange for food produced specifically as payment.

In Praise of Ants

Each enormous, fragrant peony bloom represents a significant investment of energy and resources by the plant in its bid to reproduce. These blooms are a wealth of nutrients many insects would love to feed on, thereby depriving the plant of reproduction and leaving an unsightly mess in place of that glorious flower. But nature has a solution to this problem! Peony buds produce a sweet nectar specifically to attract ants, who then attack any bud devouring insects, leaving the plant healthy and beautiful. By calling ants to come to its aid, the peony plant exchanges sweet nectar for the ants' protection.

Don't spray chemicals on your peony to kill the ants - they provide a valuable service. Instead, cut peony stems while the bud is still quite tight. Bring it indoors, and rinse the ants away. Place the stem in luke warm water and it will fully bloom in your vase.

I dearly love peonies, but I live and garden in too mild a climate to grow them. Can I enjoy them vicariously through you? :) Please take a moment to leave a comment and let me know if you will be planting peonies this fall, or if you have any questions. I am happy to help!


Peonies forum→Advice on Growing Indoor Peonies?

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I'm having a little trouble finding some more information on how to take care of potted peonies specifically (probably since they do better in the actual ground!), but I was wondering whether I should leave them outside/in our garage this winter so they get enough cold? Last winter did get into the single digits, so I'm a little concerned about freezing the plant, but I think it would be too warm in the main area of the house. I'm also not sure how much I would have to water them and whether they care about getting sunlight during this time. Most resources say to just leave them alone in the winter, but I figure if it's in a garage by itself, it might need a little more TLC.

Any advice or suggestions where I can read more would be much appreciated!!


As far as growing herbaceous in pots, I think they would do better in your garage over the winter as it would be more normal the roots. They say growing in a pot puts them in one zone colder. So your 5b would be a 4b for a peony in a pot.

I do not advise keeping the potted roots indoors as they do need chill hours to perform properly.

I hope Liz and Anya will chime in with advice, too as they are both in cold zones.


You can find a ground thermometer on Amazon and elsewhere and once you've done a couple of checks, you'll quickly develop a feel for how often you need to check the temps. You'll find that the temps are slow to change and that getting down to freezing and then returning the peonies to a cool garage can result in 12+ hours of temps below 40.

Once you get the 400 hours in, you can just leave the peonies in the garage and allow them to grow their root system. In a garage, there is a good chance that they'll push stems up early if your indoor temps are above 48 degrees. You may want to have a grow light to help them out if they push stems up early the stems really need light and you can get warped year-long leaves if you are unable to give them enough light.

EDIT: most of my experience comes from over-wintered bagged peonies. The recommendation to leave them outdoors would be a lot simpler.



Potential Problems

No flowers — Peonies that were started with small tubers or were recently transplanted (especially in the spring) may fail to develop flowers for several years. Planting the tubers more than 2 inches deep or in a shady or poorly drained location can also prevent or reduce flowering. Other possibilities include tree and shrub root competition and late spring frosts.

Botrytis blight — This is caused by a fungus that overwinters on dead leaves, stems, and roots. The disease usually appears in mid-summer, especially during cool, wet weather. Black, soft buds and wilted or soft stem tissue under the buds are usually an indication that botrytis blight is present. For control, remove diseased foliage that develops during the growing season and cut plants to the ground after a killing frost and destroy the foliage.

Phytophthora blight — This is less common than botrytis blight but can be more devastating. Black leathery spots fist occur on the buds. Stems dry up turning brown and leathery plants may rot at the ground line or crown. Control measures recommended for botrytis blight should be followed.

Leaf spots — Several fungi can cause leaf spots on peonies. Leaf blotch is a disease that usually occurs after flowering. Infected plants have small red or reddish-brown spots that later enlarge into purplish-brown blotches on the leaf surface. Destroy affected foliage as it occurs and all foliage after a killing frost.

Virus — Mosaic virus produces yellowish blotches and rings on the foliage. Infected plants are not dwarfed or deformed. Destroy infected plants to prevent spread.

Ants — Ants often will feed on the sweet, sticky secretion which covers the flower buds. Very little direct damage results from their feeding.