Shrub peonies in pots: how to grow them successfully?

Why don't shrub peonies like being grown in pots?

Shrub peonies are among the plants that are not commonly grown in pots. This is due to several reasons.

1. They develop a sturdy, deep root system, which requires space and a large volume of soil.
2. They often have a growth habit that is as wide as it is tall, with a spreading or outward habit that can reach nearly 3 metres.
3. They dislike being moved once established.
4. They have very slow growth and produce only a few branches, starting with development of their root system. You generally need to wait at least three to four years for the plant to fill out and for the flowering to become truly abundant.

If you don’t have a garden but still want to grow this plant on a balcony, a small terrace or in an internal courtyard, you will need to follow certain guidelines.

Due to their large size, shrub peonies are not well suited to container cultivation

Choosing the right varieties

To maximise your chances of successfully growing shrub peonies in pots, it is best to select varieties with the smallest growth habit, especially in width.

• the Paeonia suffruticosa ‘Wu Long Peng Sheng’, with its beautiful rose-violet flowers;
• the Paeonia suffruticosa ‘Xue Ta’, with delicate cream-white flowering;
• the Paeonia suffruticosa ‘Cai Hui’, with flowers of a bright pink;
• the Paeonia suffruticosa ‘Ri Yue Jin’, which blooms in intense red;
• the Paeonia (x) lutea ‘Alice Harding’, with lemon-yellow flowering.

Barely reaching 1 metre in spread, they will be better suited to container cultivation.

Choose a suitable container.

To successfully plant a shrub peony in a pot, start by choosing a suitable container. As we’ve said, this plant doesn’t like being moved: it is therefore essential to choose its final pot from the outset.

Turn to fairly wide models, measuring at least 1 to 1.5 metres in diameter. In terms of depth, space will also be required: allow at least 1 metre, or more. The ideal is therefore to opt for a large cultivation tub, which will stay in place.

However, ensure that the bottom is not watertight, so that excess water from watering or rain can drain away without stagnating.

A large pot will be necessary for growing a shrub peony

Finding the right exposure

Peonies do not like being moved to a new environment. Therefore you should choose a permanent location for them, especially since the size of the container will make them difficult to move.

These plants prefer partial shade, with perhaps some gentle sun, but never scorching sun. They should receive at least four to six hours of sun a day. Even though they are hardy, they do not tolerate cold winds, which can also affect flowering, as flower buds are sensitive to late frosts.

A sunny exposure is advisable

Best practices for planting

Planting is usually done in autumn.

For your bush peony, choose a well-draining substrate, but rich in organic matter. You can mix garden soil that isn’t too clayey with river sand or clay balls, as well as well-decomposed home-made compost or mature manure. You can also opt for a ready-made potting soil, such as the roses potting soil or the potting soil for containers.

1. At the bottom of the container, lay a drainage layer about 5 cm deep. Use gravel or clay balls.
2. Fill with substrate to halfway, then place your bush peony in the centre. Add more substrate until the graft point (the swollen joint at the base of the plant) is buried by about 5 cm.
3. Gently firm with your fingers to remove air pockets.
4. Water thoroughly.
5. Install an organic mulch at the base of the plant, made from straw, hay or wood chips. This helps retain the soil’s natural moisture, reducing evaporation. You can also choose to plant ferns or Hostas, which will dress the plant’s base.

Bury the graft point 5 cm below ground

How to care for a potted shrub peony

The tree peony will require some care to develop well and to reward you with a beautiful flowering.

First, it prefers cool, moist soil — soil that never dries out completely. As soon as the surface soil dries, remember therefore to water. Prefer rainwater, which is less hard than mains water, or use a balancing product. Watering should be regular from spring, and frequent in summer, especially when it is hot. Be careful not to wet the foliage when watering.

Watering needs for tree peonies

Each year, at the end of winter, apply compost, manure, horn meal or fertilisers for flowering plants (usually rich in potash). The formulations in stick or granule form should be mixed into the soil. They provide slow-release, long-lasting fertilisation. Liquid fertilisers, on the other hand, are diluted in the watering water and give a short-term boost.

Finally, arming yourself with patience to enjoy a beautiful flowering. In terms of pruning, you will simply need to remove faded flowers as they appear. Once the plant is well developed, remove only weak or crossing branches. Always remember to disinfect your pruning tools after pruning to limit the risk of disease transmission.

The tree peony is not particularly susceptible to diseases: it mainly fears excess water.