Best Companion Plants for Peonies in the Garden

Many keen gardeners wonder why their peonies grow reliably yet never produce the spectacular floral display seen in parks or traditional cottage gardens. Surprisingly, the answer is often not the variety or fertiliser, but the plants growing beside them - and the amount of space these perennials are genuinely given.

What peonies need before you combine them with other plants

Peonies are among the garden’s longest-lived perennials. When conditions suit them, they can remain in one spot for decades. Above all, they need a sunny position, or light partial shade that still provides at least four to five hours of sun each day.

Their soil should be deep, humus-rich and free-draining. Peonies particularly dislike waterlogging during winter, as their roots can quickly rot. Equally unsuitable is intense root competition from especially vigorous neighbouring plants.

“If peonies are hemmed in too tightly, fungal diseases and disappointing flowering are likely - generous air space is their most important ‘luxury’.”

One common mistake is allowing a bed to become increasingly crowded over the years. Plants grow into one another, moisture lingers on the foliage, and ideal conditions develop for grey mould and other fungal diseases. Buds may then collapse, flowers can become misshapen, or blooms may fail to appear altogether.

Three straightforward principles help when planning any planting scheme around peonies:

• Choose only perennials that enjoy sun and well-drained, relatively nutrient-rich soil.
• Do not plant noticeably taller plants immediately in front, where they will shade the peonies.
• Leave a small “pool of light” around each perennial so air can circulate freely.

Lady’s mantle and other ground cover that makes peonies shine

Once the basic conditions are right, it is time to choose companion plants for the bed. Soft lady’s mantle (Alchemilla mollis) is an especially good match. It forms a loose carpet of pleated, soft foliage topped by floating clouds of yellowish-green flowers.

This restrained colour has an interesting effect: it makes the delicate pink and white shades of peonies appear much more vivid without stealing their limelight. The pairing works just as well in a bouquet as it does in a perennial border.

Bellflowers as elegant companions for peonies

Compact bellflower species are also highly harmonious companions. Many varieties produce delicate white, blue or violet blooms in early summer. They create a light, romantic setting while avoiding competition with the peonies’ root mass.

One aspect deserves attention here: bellflowers can sometimes attract more pest insects. If you grow them together, avoid planting too densely and include a few “protective plants” nearby to discourage unwanted visitors.

Hydrangeas in the background: a stage for large blooms

Hydrangeas are excellent for providing structure at the back of a border. Their large rounded flower heads echo the shape of peony blooms without overwhelming them. Planted with some distance between them, they create a calm backdrop.

Depending on the variety, hydrangeas can tolerate a surprising amount of sun provided the soil does not dry out. During hot summer weeks, they take some of the midday sun off peonies without forming a dense canopy of shade. This particularly helps the perennials in dry years.

For a border that remains attractive over several months, peonies and hydrangeas can be combined with early- and late-flowering perennials:

• Bearded iris: usually flowers shortly before the peonies, opening their season.
• Allium: ornamental onions add architectural spherical flower heads among the perennials from late spring.
• Daylilies: take over in high summer, providing colourful accents after peony flowering has finished.

This creates a sequence of flowers from late spring well into summer, without any one plant crowding out another.

Lavender as a fragrant protective hedge around peonies

Lavender is an excellent partner for peonies, both visually and horticulturally. It enjoys sunny, free-draining sites and copes well with relatively lean soil. Used well, it forms a kind of fragrant protective hedge.

Its essential oils disturb many pests: mosquitoes, flies and some beetles, while deer and rabbits also often avoid areas planted with strongly scented rows of lavender. Anyone with peony beds along a border can position lavender precisely along that edge.

“Lavender and ornamental onions act like small security teams in a perennial bed: decorative while also deterring many pests.”

Allium species fulfil this double role too. Their slightly sulphurous scent is uninviting to many insects, yet unproblematic for people. Planted between peonies, they add height and structure without casting shade.

Plants that are best kept away from peonies

However attractive they may look in catalogues, very tall, spreading ornamental grasses planted directly beside peonies can soon cause trouble. They take away light, crowd the root zone and retain a great deal of moisture around the foliage.

Species that thrive in permanently wet, heavy soil are not a suitable match either. They keep the ground wetter for longer and create conditions in which fungal diseases can flourish. Over time, peonies respond with weaker growth and fewer buds.

Suitable neighbours	Better avoided
Lady’s mantle	Very tall ornamental grasses
Bellflowers (compact varieties)	Perennials for permanently wet soils
Hydrangeas in the background	Woody plants with strong roots immediately alongside
Lavender, allium, bearded iris, daylilies	Shallow-planted, aggressively creeping ground cover

Practical tips: planning an easy-care peony bed

In practice, it works well to treat peonies as the clear stars of the display. This means deciding on their position in the bed first, then planning the surrounding plants in rings. Keep the soil around the root area largely clear, or plant it only with very low, open-textured companions.

The next ring can contain lady’s mantle or other low-growing perennials. Around the outer edge, place a band of lavender, allium or other fragrant protective plants. Hydrangeas and taller structural plants belong behind this, or set slightly behind it.

Those just starting with peonies should take care not to plant them too deeply. The perennial’s “eyes” - the developing buds - should ideally sit only a few centimetres below the soil surface. If they are lower than this, flowering may not occur despite ideal neighbouring plants.

How the right mix pays off over time

A carefully planned peony bed develops a stable rhythm over the years. The perennials gradually grow together without crowding each other. Pest insects find fewer opportunities, as scented plants disrupt them and air circulates well through the planting.

With well-chosen companion plants, intervention is needed far less often: less staking, less summer cutting back and fewer fungal treatments. At the same time, the garden remains lively from late April well into summer - first with irises, then peonies, followed by daylilies and hydrangeas, alongside the lasting fragrant band of lavender.

When creating new combinations, it is worth considering colour and flowering times. Pastel-coloured peonies can handle strong blue and violet partners, while vivid pink or red varieties look calmer beside soft yellow and cream shades. By deliberately placing a few islands of alliums and lady’s mantle, you can create a bed with simple means that makes every peony flower look like a small painting.