The best companion plants for peonies in the garden

Many gardening enthusiasts plant peonies anywhere in a border, then wonder why the flowering falls short of expectations. Yet the key often lies not in fertiliser or variety, but in the plants growing alongside them. Choosing suitable companions helps these perennials perform far better, both visually and in terms of plant health.

What peonies need before companion plants are added

Peonies are considered easy-going, but they do have firm preferences. Ignore them and you risk fungal disease and sparse flowering. These perennials prefer full sun or light partial shade, along with deep, nutrient-rich soil that drains freely. Waterlogging in winter can severely damage their roots.

It is equally important to remember that they do not appreciate pushy neighbours close by. Planting too densely keeps foliage damp for longer, creating ideal conditions for fungi such as grey mould. The roots of vigorous neighbouring plants can also deprive peonies of water and nutrients.

“Give peonies air, light and space, and you will have sturdier plants and more reliable flowers – year after year.”

Three straightforward principles help when planning any border around peonies:

• Select only plants with similar light and soil requirements.
• Avoid placing much taller species directly in front of the perennials.
• Leave a visible, open area around each peony.

Alchemilla and more: ground cover that makes peonies shine

Once the location is right, the enjoyable part begins: designing the planting. Companions that enhance the large, lavish peony flower heads without crowding them create an especially harmonious effect.

Alchemilla: a delicate veil rather than competition

Lady’s mantle (Alchemilla) is a particularly popular choice. This tough perennial forms a loose-looking carpet of rounded, lightly crinkled leaves. In early summer, a haze of fine yellow-green flower clusters floats above them. The effect makes pink, white and pastel peonies appear even more striking, both in the border and in a vase.

Lady’s mantle remains fairly low, has shallow roots and takes hardly any nutrients away from peonies. Its foliage also covers the soil, preventing bare ground between the perennials from looking empty.

Bellflowers bring lightness to the border

Perennials with bell-shaped flowers add movement and an airy quality to a peony border. Many varieties of bellflower, and similar perennials, work well because they grow compactly and do not extend deeply into the peonies’ root zone.

There is one aspect to consider, however: bellflowers and other delicate species may attract more pests. If you wish to grow them, plan the surrounding area to include as many ‘protective plants’ as possible, whose fragrance and essential oils can act as a deterrent.

Hydrangeas, iris and daylilies for months of flowers

Peonies flower for only a few weeks, albeit spectacularly. With thoughtful planning, however, you can create a continuous display from spring into late summer.

Hydrangeas as a calm backdrop

Hydrangeas make ideal backdrop plants. Their dense shrubs and large rounded flower heads echo the shapes of peony blooms. Positioned some distance behind them, they provide light shade on hot summer days without fully covering the perennials.

The soil may be humus-rich and nutrient-rich, provided water can drain away effectively. Hydrangeas cope with sunshine when they receive enough moisture, and can be planted from autumn through to spring, depending on the region and weather.

Iris and daylilies: passing on the flowering baton

Staggering the flowering periods is especially effective:

• Bearded iris open their flowers shortly before the peonies. Their colours create a link between spring and early summer.
• Peonies then take centre stage with their large, scented blooms.
• Daylilies carry the display into summer, when peonies are showing more foliage than flowers again.

This creates borders without obvious visual gaps. Selecting varieties in similar shades produces a calm, refined look. Those who prefer contrast can deliberately use complementary tones, such as purple iris alongside soft-pink peonies.

Lavender as fragrant protection: attractive and useful

Lavender suits peonies surprisingly well, as long as the soil is not overly heavy or wet. Both enjoy sunshine and free-draining earth. This subshrub forms dense rows that are ideal along border edges.

“Lavender provides more than colour and fragrance – it acts like a living protective barrier against many garden pests.”

Its powerful scent unsettles numerous insects and even larger visitors. Mosquitoes, flies, some sap-sucking pests and often deer too avoid the smell. Planting lavender along the border edge creates a naturally scented barrier, allowing peonies to develop in a more relaxed setting.

Allium species play a similar double role. Their spherical flower heads are decorative, while their sulphurous scent deters various insects. Planted among peonies, they add vertical interest while providing a degree of protection at the same time.

Which plants do not belong in a peony border

Mixed borders may be beautiful, but not every fashionable plant makes a suitable neighbour. A common mistake is using highly vigorous ornamental grasses that spread through dense root balls. They draw heavily on the soil’s water and nutrients and deprive peonies of space and air.

Species that prefer permanently wet, heavy soil are also poorly suited. They encourage exactly the constantly damp conditions in which fungal diseases can easily take hold on peonies. The perennials may then develop limp stems, rotting buds and brown patches on their foliage.

Practical examples: what a successful peony border looks like

Anyone new to growing peonies can use simple combinations as a guide. For example, place two or three peony clumps in the centre, slightly offset from one another. Add a loose band of lady’s mantle in front, interspersed with individual allium globes. Position a low hydrangea shrub behind them and a strip of lavender at the edge.

Another arrangement focuses more strongly on successive flowering: a row of bearded iris, with peonies behind it, alliums in between, and hydrangeas at the back of the border. Daylilies fill the front area and flower later. This produces a border that remains colourful from May into August.

What amateur gardeners should also bear in mind

Newly planted peonies require patience. These perennials often need two to three years before they show their full potential. During that period, especially open planting is worthwhile so they can establish without stress. The surrounding planting can be made denser later, but air circulation must always remain a priority.

When planting, it helps to allow for the space a peony will require in five to ten years. Mature clumps can become impressively large. Planning too tightly means facing an overcrowded border only a few years later, where fungal diseases gain a foothold more quickly.

One further aspect is often underestimated: soil preparation. Deeply loosened ground improved with compost, but never wet, is invaluable for peonies. In heavy soils, drainage such as gravel considerably reduces the risk of root rot. Those who put in this effort at the outset will be rewarded for many years with healthy, abundantly flowering perennials.