Peonies: the best companion plants for an impressive border

Many garden owners plant peonies wherever there happens to be space in a border, then wonder why the result is nowhere near as striking as a stately garden display. The secret is rarely the cultivar; it is almost always the plants around it. Understanding the requirements of these perennials and selecting suitable companions will bring far more out of every plant, both visually and in terms of plant health.

What peonies need before adding companion plants

Peonies are among the longest-lived perennials for the garden. They can remain in one position for decades, but will only flower abundantly when their basic needs are met. The site determines whether they produce a spectacular annual display or manage only a few lacklustre buds.

• Plenty of sun: at least six hours of direct sunlight daily is ideal.
• Deep, fertile soil that drains water effectively.
• No winter waterlogging, as this causes the roots to rot.
• Sufficient space between plants so foliage can dry quickly.

When perennials are planted too closely together, moisture lingers in the foliage for longer. Fungal diseases such as grey mould can then spread quickly, damaging buds and leaves. Although an overcrowded border may look “full” in its first year, it often leads to unhealthy perennials later on.

A clearly open ring should be left around every peony so that air and light can reach every shoot.

Competition below ground matters too. Vigorous roots from immediately adjacent plants can deprive peonies of water and nutrients. When planning a border, it is therefore worth taking a second look at how strongly the intended companion plants grow.

The best companions for peonies: gentle contrasts, not competition

Alchemilla: green clouds that make peonies shine

Alchemilla, commonly known as lady’s mantle, is considered one of the finest companions for peonies. This perennial forms dense, low cushions of soft foliage topped with delicate clouds of yellow-green flowers. That exact shade makes the pastel and pink tones of peonies stand out, both in the border and in a vase.

• It remains low enough not to deprive the peony of light.
• It spreads moderately, leaving room for neighbouring roots.
• It fills foreground gaps without crowding the peony clump.

For anyone who enjoys cutting flowers, lady’s mantle and peonies make an almost unbeatable classic combination: the soft flower clusters frame the large blooms and add structure to a bouquet.

Bellflowers and other perennials with nodding blooms

Bellflowers have a delicate, romantic character and visually complement the full, rounded flowers of peonies perfectly. Many varieties stay relatively compact and do not grow up into the peonies’ height. This creates a balanced arrangement in which the peony remains the focal point.

One consideration requires a little attention: some bellflower species are more susceptible to pests. This is not a major issue close to peonies as long as aromatic plants such as lavender or ornamental alliums are also included in the border. Their scent unsettles many insects, acting rather like small protective shields.

Hydrangeas as a strong backdrop

Hydrangeas work particularly well at the back of a peony border. Their large flowerheads echo the rounded form of peony blooms while extending the flowering interest into late summer.

Planted with some distance between them, hydrangeas create a calm, flowering backdrop without shading the peonies.

Spacing is essential. If hydrangeas are too close, they reduce available light and take up too much water. Positioned a little further behind, however, they cast light shade during the hottest weeks, relieving the perennials without “covering” them.

Colour succession: keeping the border in flower from spring to summer

Peonies have a comparatively brief but intense flowering season. Thoughtful planting can frame this period so that there are hardly any gaps in the border.

Time	Plant	Role in the border
Spring	Bearded iris	Flowers shortly before the peonies and signals the main display to come.
Late spring / early summer	Peonies	The highlight, with large, showy blooms.
Early summer	Ornamental allium (Allium)	Adds vertical accents among the perennials.
Summer	Daylilies	Take over the colour display as peonies finish flowering.

Bearded irises usually flower shortly before peonies. Their upright stems introduce the first height into the border. Once their display fades, the peonies take centre stage. Ornamental alliums stand between them like small upright brushes, drawing the eye upwards with spherical flowers on slender stems.

As peonies shed their final blooms, daylilies come into their own. Their trumpet-shaped flowers open anew each day and provide colour for several weeks, often within the same colour palette as the peonies. The border therefore appears to continue seamlessly.

Lavender and ornamental alliums: scented protection for healthy peonies

Lavender is often seen as the essence of southern gardens. In a peony border, it performs several roles at once. Like peonies, it thrives in sunny, free-draining conditions. It forms compact rows or cushions, and its strong fragrance helps keep many pests at bay.

• It repels midges, flies, certain aphid species and even browsing by wild animals.
• Its blue-grey foliage visually softens the edge of the border.
• It enhances pink and white peony shades with a cool contrast.

Used as border edging, lavender acts as a natural barrier. The area around the peonies remains calmer, experiences less browsing and is often less prone to fungal problems because air circulation stays good and foliage dries swiftly.

Ornamental alliums combine decorative value with protection. These bulbs provide not only architectural globe-shaped blooms, but also release a slightly sulphurous scent that many insects avoid. Planted among peonies, lady’s mantle and daylilies, they create interesting changes in height without any plant taking light from another.

Plants that are less suitable for peonies

While many combinations look harmonious, some plants simply do not suit peonies. Tall, vigorous grasses and species that prefer permanently wet ground are particularly problematic.

Anything that keeps the soil consistently heavy and wet, or spreads with great force, is rarely a good match for peonies.

Tall, spreading ornamental grasses develop dense root systems that compete with peonies for water and nutrients. They can quickly overhang the border, cast shade and trap moisture inside the clumps. This is precisely where fungal infection often begins.

Plants that prefer pond margins or very heavy clay soil also make conditions difficult for peonies. They draw more water, keep the ground wet for longer and therefore encourage rot and fungal diseases on the perennials. Anyone who loves peonies is better off placing these species in a separate part of the garden.

Practical tips for an impressive peony border

Whether creating a new planting scheme or reshaping an established border, a few straightforward measures will make life easier for peonies:

• Do not plant peonies too deeply: the buds should sit only a few centimetres below the soil surface.
• Allow at least 60–80 centimetres between a peony and the next larger perennial.
• Do not allow dense ground-cover plants to grow directly against the stems.
• Remove spent flowers promptly so that wet, fading flower remains do not hang on the plant.

A border planned with a considered colour scheme almost automatically appears well maintained. One tried-and-tested combination for a home garden is white or pale pink peonies in the middle of the border, with lady’s mantle and lavender in front, and hydrangeas or smaller shrubs behind. Add a few ornamental allium globes and individual daylilies between them, and the result resembles a professionally designed display garden.

Going one step further: soil preparation and care

Peonies reward every effort invested in preparing the soil. Before planting, it is worthwhile to loosen the ground deeply and incorporate plenty of well-rotted compost. In heavy soils, coarse sand or fine gravel helps water drain away more quickly. This can significantly reduce later problems with rot.

In spring, these perennials benefit from a moderate feed, such as an organic balanced fertiliser or compost. Excessive nitrogen, however, mainly encourages leafy growth and makes plants softer and more vulnerable. A restrained but regular application every one to two years is the better approach.

Once combined with the right neighbours, peonies require remarkably little care over the years. Cutting back foliage in autumn, applying a little compost in spring and occasionally thinning the immediate surroundings are usually all a well-planned peony border needs. The reward is dense clumps with impressive flowers, set within a plant community that renews the display every year.