Peony – the thornless rose

Anu Nurmsalu, Kaevandi Farm

I’m sure many of us can recall the beautiful peonies growing in our grandmother’s garden. Generally, peonies are pink or white, but the early short red peony is also well-known. However, the world of peonies is a lot richer than that.

There are nearly 40 types of peonies – Paeonia in Latin. Naturally, these fancy plants grow in Central and Southern Europe, Caucasia, Asia and North America. 

Peony cultivation is considered to be the beginning of ornamental gardening in China. Originally, the common garden peony (Paeonia lactiflora) was used in China as a medicinal plant. The root bark was used to treat fever, promote the functioning of the liver, cool a person down, and strengthen the blood. In a while, the peony was gaining popularity as a decorative plant. The Chinese used the valuable root in the exchange of goods, so the peony travelled to Japan. The Chinese enjoyed the large and fancy composite flowerheads, whereas the Japanese cultivated a much simpler simple flower with a ring or two of petals, and the magnificent stamens in the middle, together with modified petals or stamenoides – also known as the Japanese peony. Another achievement by the Japanese are the hybrids of tree peonies and grassy peonies. The credit for this went to Toichi Itoh before the year 1950 and he was the author of the current Itoh hybrids known to us: e.g. the yellow-flowered Barzella Yellow Crown and to some extent, the greenish Green Lotos and Green Halo. 

The rich world of peonies

Over the past years, the yellow peony has been a favourite of gardening enthusiasts; for example, the types Hadrian’s Villa and Hierapolis. A new direction in breeding is tricolour blooms – the types Federica Ambrosini, Glory of Rome and Kantharos, for example. The type Candy Stripe has a different pattern on every petal.

Paeonia suffruticosa is known as tree peony and affects the Itoh hybrid a lot as well, namely in that it gives the plant large and luscious flowers and leaves similar to those of the tree peony. 

Popular in Mongolia, Kazakhstan and China, the Paeonia anomala grows only one purple or pinkish simple flower per shrub, just like Paeonia banatica, which originates from Hungary, Serbia and Romania. The low Paeonia wendelboi loves hilly slopes, rocks and sand.

Paeonia Veitchii-Veitchi surprises with its luscious leaves and bell-shaped blossoms.

Often, Paeonia bergiana – the Swedish peony, and Paeonia tenuifolia – the fernleaf peony, are mixed up. The Swedish peony is taller than the fernleaf and its leaves are wider, whereas the fernleaf has thinner leaves reminiscent of dill. Our northern neighbours have aptly named it Tillipioni.

Peonies are distinguished according to their flower shape and blooming time:

• according to flower shape, peonies are divided into single, Japanese (anemone), semi-double and double; 

• the double, in turn, are divided into rose and half-rose, half-spherical and spherical, and petalled peonies.

• Size of flower. A giant flower is one with a diameter of more than 18 cm, whereas a small one is smaller than 12 cm. Medium-sized flowers are 13–17 cm.

• Blooming time – from very early up to very late. Usually, the peony starts blooming between the first ten days of June and the first days of July.

What does a peony like?

A peony generally likes a sunny, rich and moderately humid permeable soil. The density of planting and movement of the air are very important: a biological community that is too dense and has insufficient air supply causes fungal diseases to spread. When selecting the planting site, the specific type should be proceeded from. 

There are types that prefer hillier terrains and should therefore be planted on east and west direction slopes. High groundwater level and still surface water can be fatal for peonies because the peony’s roots go very deep into the ground. To avoid this, the plants are planted on a high mound of soil with the bottom layer broken up and drained. Soil acidity should be neutral or slightly acidic. Add mold compost and pebbles into the planting hole to help the water move. If the peonies are struggling, check the planting soil. If it is dense, it should be aerated and compost added. Clayey soils are richer and develop beautifully colourful and luscious flowers. Sandy soils are poorer in nutrients and may cause problems. Fertilisers could be used in the proportion nitrogen-phosphorus-potassium 10:10:10 or 15:15:15.

As a peony remains in its growth site for years (up to 100 years), the site should be picked carefully. I have established the growth site into the lawn and planted them in 2–3 rows with 1.2–1.5 metres between them. Soon, it turned out to be inconvenient to maneuvre between them with a lawnmower, so I covered the ground between the shrubs with cardboard boxes and spread a thick layer of mulch on top. Avoid planting peonies near large trees because the roots of these trees drain the nutrients from the soil, the bushes start bending towards the light and the stems will remain short.

How to get beautiful luscious flowers?

A peony bush starts forming flower buds for the next year in July and August. A hot and dry summer is followed by little blooming – the bush is able to grow the main flower and one lateral bud. Usually, the stem has a main flower and, depending on the variety, four or more lateral buds. Therefore, the bush needs to be abundantly watered in dry times so that flowers could be formed: up to 4 bucketfuls of water per bush. After blooming, clean up the petals fallen on the ground to avoid moulding and rotting. The flower part should be cut back; most of the varieties need support as well. A tip to gardeners: do not tie the bush with a rope in the middle like a sauna whisk. The bush needs air and the heavy flowers need support.

It is often thought that the bush can be cut down after blooming. Any systematic activity like this destroys the plant. The peony can be cut back only in the autumn when the first colds have made the stems fragile; it is advised to burn the stems because fungal diseases are not destroyed in compost.

Diseases and pests

In the spring, lively hustle and bustle can be seen on peony buds. Ants are attracted to the nectar excreted by the buds. But on the whole, ants do not cause any damage to the plant. However, the peony is sensitive to plant diseases.

The formation of grey mould on peonies is promoted by a cool and wet spring. Near the ground, the stems get softer, start rotting, the buds will not open and are covered with mould. The stems collapse onto the ground and roots may get infected as well. Earlier varieties are more sensitive.

Conditions favourable for diseases:

• wet and acidic soil

• shaded growth site

• dense planting

• rainy weather, sudden temperature changes

• lack of potassium, excessive nitrogen.

Phyllosticta paeoniae – brown spots about a millimetre in size appear on the lower leaves, get larger by the autumn, turn black, and holes form in the leaves. Damages over a longer period result in small or undeveloped flowers.

Cronartium flaccidum – the disease is promoted by warm, humid and rainy weather. The leaves are twisted and dry, yellowish-brown spots and spore pads appear on both sides. The winter spores hibernate on peony leaves.

Tobacco rattle virus – unclear veined (yellow up to light green in colour) semi-circles or circles appear on the leaves. The leaves become wavy, the flowers look undefined; often, the buds dry up and the shoots wither up. The virus spreads with tools, and greenflies “help along”. The diseased parts of the plant must be removed and burned and the tools disinfected. Any suspicious-looking bushes should not be shared with others.

Mostly, peonies are healthy and resilient plants. If planted correctly, fertilised sufficiently and cared for diligently, they bring joy to the owner for years and years. 

In Estonia, large peony collections can be seen at Kaevandi Farm and Energy Herbal Farm, and the University of Tartu Botanical Garden.