How to grow peonies – The Peony Society (2024)

How to grow peonies

For those new to peony gardening, here’s some advice to get you started and place you firmly on the road to peony addiction. This is a general overview and for more details you can simply search the site or go to the American Peony Society website.

The following topics will be written about:

• What peonies are there?
• Where, when and how to plant them
• How to care for them
• Peony diseases
• Where to obtain plants and recommended varieties

What peonies are there?

The number of peony varieties is large, very large. The International Cultivar Registration Authority (ICRA) for peonies is the American Peony Society (APS). Their registry has some 5,000 varieties, but many others are never registered, mostly from China and Japan, so perhaps about 10,000 varieties have at one time or another been around. The great majority of these have vanished over time and are no longer commercially available, but the number you can choose from nowadays is still staggeringly large.

Now, all peony varieties are derived from wild ancestors. Big discussions arise over how many paeonia species there are, but somewhere between 30 and 50 will be about it. They fall into two large groups. The herbaceous ones, those are perennials that die back each and every year, and the shrubby ones, that merely loose their foliage and keep their woody stems and branches. The latter are also known as ‘tree peonies’, although that is surely exaggerating. All woody peony species originate in China and shrubby peonies are there referred to as the ‘Queen of Flowers’. Within the shrubby peonies there are also different groups. The most widely known are the suffruticosas, those are Chinese tree peonies bred over hundreds of years. Usually double flowered, they grow well in some warmer, drier locations but lack yellows. In more humid climates they tend to grow less well. Then there are Japanese tree peonies, also lacking yellows, but usually less double and having better upright habits. There are also lutea-hybrids. These are the result of crossing the two groups mentioned before with the yellow P. lutea (P. delavayi). This resulted in yellow and orange tones, but quite often they also inherit a somewhat hanging flower from the wild species. Another very promising group that is only slowly getting known are the Ziban Mudan peonies, those are tree peonies deriving from P. rockii. P. rockii has a conspicuous flare in its’ petals and thus the hybrids are also known as Rockii-hybrids or ‘flare tree peonies‘. They are hardier and easier to grow compared to the other groups.

Some shrubby peonies:

Herbaceous peony species on the other hand can be found in many places in the Northern temperate zone. Not all of them have been used extensively in hybridizing, most perennial peony cultivars are Paeonia lactiflora, thus deriving from that one species. They are often also known as Chinese peonies, or Paeonia sinensis, because most early cultivars came from there. Later on, in the 19th century, French and British hybridizers have also introduced many cultivars; the most widely grown are from that time period. Examples include the pink Sarah Bernhardt and white duch*esse de Nemours. Most, though not all, lactiflora cultivars have double flowers with sidebuds. In the 20th century some hybridizers, most notably A.P. Saunders, have embarked on using more species to get more colours, different foliage and a wider flowering period in the herbaceous peony group. These hybrids thus include colours not found in the lactifloras, like the “Corals”, which change colour from dark pink, over orange to yellow when blooming. Nowadays most new peony registrations are hybrids, with lots of very attractive colours and many doubles which were rare to come by in the earlier years of hybridizing with those new species.

Some herbaceous peonies:

The last decades intersectional hybrids (or ‘Itoh’ peonies, named for the first hybridizer succeeding) have come to the market. Those are the result from crossing herbaceous peonies with shrubby ones. They act like perennials, dying above ground each year, but have the foliage of the shrubby ones. Many of those are yellows, as a true deep yellow is not to be found in the herbaceous ones and they thus fill in that void. Often these intersectional hybrids show great vigour and disease resistance, so from a gardener’s view, they are highly recommended plants. Lately some breakthroughs in hybridizing have finally resulted in offspring from these intersectionals and it can be expected that more intermediate forms will show up in the future, hopefully with the health and growth characteristics of the intersectionals.

Some intersectional peonies:

Now there are many ways to classify these peonies. One would be time of flowering. Usually several of the species will flower first, followed by shrubby peonies, then the hybrid perennial ones together with the intersectionals, whilst the lactiflora cultivars are usually the last ones to flower. Nearly all catalogs will have an indication of flowering period, so you can simply pick several varieties to have blooming peonies in your garden for several weeks. The standard comparison for blooming period is usually Red Charm. The earliest blooming species (P. kesrouanensis, P. turcica, P. caucasica, P. mairei, P. ostii) bloom about a month before it, whilst the last flowering lactifloras, Elsa Sass for example, bloom a month after it, which makes some two months in all.

Another classification could be by flower form. The double flower with many layers of petals is the most well-known and popular, but there are also bomb-doubles where there is one row of large petals surrounding a whole bunch of erect petaloids in the middle. Petaloids are stamens transformed into petals. There are also single flowered peonies, semi-doubles and Japanese/anemone flowered types. The latter are flowers where the stamens are transformed in smaller (Japanese) to wider (anemone) petal-like staminodes.

Peonies also differ in height, fragrance, foliage, flower colour and so many other characteristics. Whatever you prefer there is almost certainly a cultivar that fits it and there are many specialized peony nurseries, with an online presence, in the world where you could have a look.

Where, when and how to plant them

Where and how should you plant your peonies? First of all, peonies need a cold winter chill to start growing in the Spring. Thus they are confined to the temperate zones of this world. They can take quite some cold, some varieties can grow as far north as the Kola peninsula of Russia (the top of Scandinavia) and some grow in Northern Africa, although on higher elevations. There are differences between cultivar (groups) when it comes to chilling requirements and cold hardiness. The shrubby Rockii-hybrids can take the most cold, together with P. anomala in the herbaceous group. Some Mediterranean herbaceous species do better in warmer, drier places.

The best time to plant peonies is in Autumn (September, October). And the best plants are bought bare root. Thus no containerized plants bought in Spring as you will find most often in your garden centre. Peonies don’t grow too well in containers and the roots will usually have been cut off to make them fit into the container. Only if they are in exceptionally large containers can peonies thrive, this is only very rarely the case. Bare root plants that you’ll plant in Autumn will on average be larger and have time to settle in, making new very fine roots that same season before Winter sets in. Time and time again trials have shown that peonies planted in Fall outshine peonies planted in Spring. That is also the reason that most specialized peony nurseries only sell them bare root.

Most peonies need full sun for at least several hours a day. There are some peonies that do better in shade, but those are a minority. If in shade most peonies will fail to bloom or will deliver less and smaller flowers. Some peonies that do well in shade: most of the species, especially P. japonica; some hybrid varieties like the ‘lobata of Perry hybrids’ created by A.P. Saunders (Cytherea, Red Red Rose,…).

Before planting it is a good idea to add some balanced fertilizer to the soil. There are chemical fertilizers available, but organic ones are preferred because those also contain micro-nutrients, next to better-known Nitrogen (N), Phosphate (P) and Kalium (Potash) (K). Old cow manure (not fresh) is an ideal fertilizer for example and it will give nutrients for several years to come. Never apply such organic fertilizer directly upon the plant, but apply it around the plant, otherwise you might kill it.

As to the acidity of the soil (PH), it is often assumed that they will need a slightly acidic to neutral soil, but in fact most peonies grow best in slightly alkaline soil with a PH slightly above 7. You can add lime to the soil to get to a slightly higher PH.

What is of utmost importance when planting peonies is the soil drainage. What they hate most is ‘wet feet’. If you plant them in a spot where water tends to remain too long after a downpour, you are nearly certain to loose your plants to rot. How to test whether your intended planting spot is adequate in this respect is described by world-renowned peony hybridizer and grower Don Hollingsworth:

“For an unknown site, you can determine the drainage characteristics by a percolation test, as might be used to evaluate a site for a septic tank absorption field. Dig a hole 18 inches deep, fill it with water enough times that the surrounding soil is well wetted. Then refill it and time how long it takes for the water to get away. An hour or less suggests an excessively droughty site. Three to six or ten hours may work very well with an ordinary calendar of rainfall. However, if water remains in the hole after 24 hours, you have a chronic wet‐land. Either install mechanical drainage measures to change the situation or select another site for your peonies. Raised bed strategies may also be of help, depending upon site and design.”¹

Another point of attention is depth of planting. Now here’s an important difference between herbaceous and shrubby ones. Herbaceous ones need to be planted shallow, with only some 2-5 cm of soil above the buds. Shrubby peonies on the other hand need to be planted deeper. Most are propagated through grafting where a scion is taken and attached to another root. The point where they are attached needs to planted some 10 – 15 cm below soil level because otherwise there is a large chance of the root sending up its own shoots instead of the intended scion. Intersectionals can be planted as herbaceous ones, thus shallow.

Something else to keep in mind is that you should never plant peonies again where they have grown before. Whilst they grow well for perhaps a hundred years in the same spot, if you dig them and plant another peony at that same place, you’ll soon find out that it will not grow well. It will remain shorter and deliver less stems and flowers. This is known in the trade as ‘peony replant disease‘, the cause of it is still somewhat uncertain, but trials have shown that even after a seven year wait the problem still arises. So if you really need to plant another peony at that same spot, you’ll have to remove the old soil and replace it with fresh soil.

The distance between plants depends somewhat on cultivars. If you want them to ‘close’ the soil, some 70 cm will be ideal. If you give them more space, say 100 cm, they will receive more wind and be less prone to botrytis disease.

After planting you can mulch them with a good compost to suppress weed growth. This will also result in soil moisture remaining more stable and will add some nutrients.

How to care for them

Now that you’ve planted your peonies, you’ll need to be rather patient. It will usually take some 3 years before you have a large plant and some 5 years before it is fully mature. Fully mature as meaning that from then on it will produce more or less the same number of stems each year. In the peony world you’ll often hear: first year they’ll sleep, second year they’ll creep, third year they’ll leap. The first year you may consider yourself lucky if you have any flower at all, normally you’ll have only one or two short stems and if you have a flower it will be less double and smaller. The second year you may have normal shaped flowers, but it is only from the third year onwards that you will really be enjoying your work done in the past.

As to caring for them, they are relatively easy. An occasional fertilization from year to year and watering when dry (especially the first year). What is quite important is to cut herbaceous ones down in Autumn, when the foliage has died. Do not pull those dead stems because the new buds for the following year are already present on the root and they are growing next to that old stem, so you might damage them by pulling instead of cutting. Cutting them off at some 5 to 10 cm above ground has shown to decrease botrytis disease the next season. Remove that dead foliage because fungal spores remain on them and would otherwise infect the new shoots in Spring. Shrubby peonies only loose their leaves, so that’s all that need to be removed there. You could prune your woody peonies if needed, to give them a better shape and to remove dead stems. If in a harsh Winter all aboveground growth of your shrubby peonies has died, you will find that new shoots will grow in Spring, thus you should not hesitate to remove those dead stems.

Peony diseases

As with all plants there are some diseases that may make your peonies grow less well. There are a few very common diseases that we’ll treat here:

Botrytis is the most common disease which you’ll find on peonies. It is a fungus that has a huge host range and is omnipresent. Spores will germinate when there is some 24 hours of continous high humidity. Afterwards temperature makes the disease go faster or slower. It will attack healthy tissue and kill it because it needs dead tissue to feed on. It can attack at all stages of growth. When shoots break though the ground it often attacks the bottom of the stem, resulting in soft brown tissue and stems falling down. Later on it may attack the foliage, resulting in brown edges or brown dead tissue again. It can also attack the flower buds, usually starting below the bud where it is attached to the stem and slowly advancing upwards through that bud. Finally it can also attack the flowers when blooming, first showing as small dots on the petals, to advance into petals rotting away. Remedies are spraying with fungicides of course, but spacing them further apart so that the foliage dries up faster is an excellent preventive course. Removing dead tissue in Winter is also a good preventive action as it will remove most of the fungal spores. If you happen to live in a region with drier Springs or with a rather constant drying wind, you will hardly have any difficulty with the disease.

Botrytis

Leaf nematodes (eelworms, aphelenchoides fragariae) are another quite common pest that can infect your peonies. Although widespread all over the world, it is seldom as such acknowledged. The pest can only be seen through a microscope and thus you’ll have to look for telltale signs of its presence. Distorted foliage, fewer stems, shrunken buds and deformed flowers are all results of it eating away at the plant. You can also have a look at buds that don’t seem to develop. Whilst most often this is a result of water shortage, it can also be the result of nematodes. When they simply dry up and remain small you have water shortage damage; when they rot from the bottom upwards, you have botrytis; when they are completely soft and wet, becoming fully rotted, you have frost damage; when they seem to be eaten partially inside, you have leaf nematodes. After flowering the easiest sign of telling what you have is looking at the leaflets, when there’s dead tissue that ends at the veins, you have this pest because they cannot simply pass them (if that dead tissue goes over the veins, it is usually botrytis). Foliar nematodes spread during damp weather or rains, then they come out of the leaves and travel further. This results in the average spread of the pest, it starts with one plant and the following years you’ll notice that adjacent plants also start showing these symptoms. If you have a whole field of peonies, it makes for a large circle of infected plants. There’s not really much that can be done against it, except for some rather severe insecticides. The best a gardener can do in that case is simply cut down the infected stems (or the whole plant) when it is obvious the nematodes are the cause. This will set back the plant but will also remove most of the nematodes. Perhaps not all as some are already present in the buds for the next year. However the infestation will have dramatically decreased and you may get off by simply removing one or two stems the following year. A hot water drench applied to the bare roots may also kill this pest, but that can only viably be done by a professional nursery or specialized company because only a fraction too high in temperature can kill the plant whilst a fraction too low will simply not kill the pest. Some cultivars are more prone than others, although none are probably fully resistant. Coral Sunset and Old Faithful are two varieties that easily get it. The intersectionals and shrubby peonies seem to be tolerant, which is not the same as resistant, and don’t show any damage usually.

There are of course many other pests and diseases, but over the years these have been the most common in our experience. If you are interested in peony diseases, the APS has a nice page with images of peony diseases.

Leaf nematodes

Where to obtain plants and some recommended varieties

As you will surely have noticed by now, we are strongly encouraging you to buy peonies bare root in Autumn from specialized peony nurseries. The average garden centre will unfortunately deliver only mediocre plants, the exception notwithstanding. A specialized peony nursery will deliver you larger plants, true to name (a big problem in the peony trade) and you’ll have the largest choice of cultivars to pick from. As peonies are relatively expensive plants and they can last a lifetime, it is a wise decision to go for quality. The APS has a list of suppliers, have a look there and order soon because the most wanted varieties tend to sell out quick at most nurseries. Soon means January/February for most nurseries, delivering their plants in Autumn. A good division will have 3-5 or more eyes, it depends somewhat on variety as there are some that are more floriferous than others. The standard traded root division wholesale is 2-3 eyes, but those will take another year to grow into nice plants and the smaller the more difficult to grow them. Those smaller ones are usually those that you’ll find in your retail store or in pots in garden centres.

If in due time you grow a nice collection of peonies, you could consider digging and dividing the plants to multiply them. Perhaps there’s an expensive or rare cultivar in your garden that you would like to get more plants of. Or you could also make some friends happy by providing them with some new garden gems. Digging and dividing is done in Autumn again, after the foliage has died. Dig the plant, wash of the soil and then simply cut through the plant, leaving some crown with at least 3 eyes and a few roots on every division, then replant. If you need to store them for a while, be careful of roots drying out, place them in some dry peat or spaghnum moss and keep them at ambient temperatures. At outside temperatures because in cold storage they will already accumulate some of their required chilling and may afterwards start growing too soon during some warmer days in the midst of Winter.

Be sure to browse the catalogs and choose whichever variety you prefer yourself, but here are some we could recommend. Again the APS has a list of recommended varieties, the so called Award of Landscape Merit, listing floriferous, healthy cultivars with strong stems that don’t flop. Each cultivar has an extensive description so you can be well informed objectively. There are currently more than enough varieties that stand up well, so you should never be satisfied with a cultivar that needs staking.

We don’t really recommend buying the newest varieties available, some are currently ludicrously expensive and not all have as yet shown their worth. There are many golden oldies and within registrations of the last decades many good ones are also available.

Within the ‘golden oldies’ we could recommend Shirley Temple, a blush to white double with a strong fragrance and upright stems. Dr. Alexander Flaming is a double dark pink with strong upright stems. For a good double red ‘Red Charm’ is still a good one, early flowering with large blooms, it may benefit from some additional fertilizer. For a very large white, pink in blush, you could also go for Gardenia. Sarah Bernhardt, the most famous one (and the cheapest) is not really recommended. Whilst it is very reliable, an easy grower and has very attractive flowers, the stems are too weak and give it a little bit of rain and the stems are laying flat on the ground.

From the more recent ones there’s Petite Elegance, a semi-double lactiflora, early flowering, short of stature and nice fragrance again. Or The Fawn for a double pink with large flowers on sturdy stems. If you go for really sturdy stems, there’s also no escaping Old Faithful, a very attractive deep red. Coral Sunset is probably the prettiest of the corals and has a better plant habit than the rest of them. For a good hybrid early white, the semi-double Grand Massive is a good new kid on the block. In pale yellows the double Ballerina is outstanding and has conspicuously attractive foliage in Spring. Tranquil Dove is another plant with attractive foliage, easy growing and white to pale pink flowers with a darker edge.

Within the intersectionals Garden Treasure is a floriferous very agreeable fragrant yellow that flowers over an extended period, whilst First Arrival is a very attractive pink cultivar.

For shrubby peonies we have admired the single lilac pink Anna Marie and the semi-double huge pale pink Hana Kisoi.

Species peonies are more difficult if you have no former experience growing them, but some of the easiest ones are P. peregrina and P. caucasica. Also recommended, if you live in a colder climate at least, is the pink P. anomala. In many cases though it’s better to go for some alike hybrid: Early and Late Windflower for example are far easier to grow than P. emodi.

If you have any remarks, please feel free to add your comment below.