Peonies: the best companion plants for spectacular blooms

Anyone who loves peonies can make their floral display positively explode with the right border companions – provided a few basic rules are met.

Many amateur gardeners wonder why their peonies grow reliably yet never produce the spectacular burst of flowers seen in parks or traditional cottage gardens. Surprisingly, the answer is often not the cultivar or the fertiliser, but the plants growing immediately 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 longest-lived garden perennials. When conditions suit them, they can remain in the same spot for decades. Above all, they need a sunny position or light partial shade, receiving at least four to five hours of sunshine each day.

The soil should be deep, rich in organic matter and free-draining. Peonies strongly dislike waterlogged winter ground, as their roots can quickly rot in these conditions. Heavy root competition from particularly vigorous neighbouring plants is equally unsuitable.

“If peonies are planted too closely in, fungal diseases and disappointing flowering become a risk – generous air space is their most important ‘luxury’.”

One common mistake is allowing the border to become increasingly crowded over the years. Plants grow into one another, moisture lingers on the foliage for too long, and the result is an ideal breeding ground for grey mould and other fungi. Buds may then collapse, blooms become distorted or flowers fail to appear altogether.

Three straightforward principles help with any planting scheme around peonies:

• Choose only perennials that enjoy sun and well-drained, reasonably fertile soil.
• Do not place substantially taller plants directly in front, where they will shade the peonies.
• Leave a small “pool of light” around each perennial so air can circulate freely.

Alchemilla and other ground cover that makes peonies shine

Once the basic conditions are in place, it is time to choose the finishing touches: the border companions. Soft lady’s mantle (Alchemilla mollis) is an especially good match. It creates an airy carpet of softly pleated foliage, topped by clouds of yellow-green flowers.

Its restrained colour has an interesting effect: it makes the delicate pink and white shades of peonies appear considerably more vivid without stealing their spotlight. This pairing works just as well in a cut-flower arrangement as it does in a perennial border.

Bellflowers as graceful companions

Compact-growing bellflower varieties also look highly harmonious alongside peonies. Many 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 detail deserves attention here: bellflowers can sometimes attract more pest insects. If you combine them, avoid overly dense planting and include a few “protective plants” nearby to deter unwanted visitors.

Hydrangeas in the background: a stage for large blooms

Hydrangeas are excellent for adding structure to the rear of a border. Their large rounded flower heads echo the shape of peony blooms without overwhelming them. Planted with some distance between them, they provide a calm backdrop.

Depending on the variety, hydrangeas tolerate a surprising amount of sun as long as the soil does not dry out. During hot summer weeks, they take some of the midday sun off peonies without creating a dense canopy of shade. This is particularly beneficial for the perennials in dry years.

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

• Bearded iris: usually flowers shortly before peonies, introducing their season.
• Allium: ornamental onions bring architectural spherical blooms among the perennials from late spring.
• Daylilies: take over in high summer, adding colourful accents once peony flowering has finished.

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

Lavender as a fragrant protective hedge around peonies

Lavender suits peonies exceptionally well, both visually and horticulturally. It thrives in sunny, free-draining places and copes with relatively lean soil. Used thoughtfully, it forms a kind of fragrant protective hedge.

Its essential oils disturb many unwelcome visitors: mosquitoes, flies, some beetles, and even deer and rabbits often avoid areas edged with strongly scented rows of lavender. Where peonies grow in border-edge beds, lavender can be planted precisely along that outer edge.

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

Allium species fulfil this double role too. Their slightly sulphurous scent is unappealing to many insects but causes no issue for us. Planted between peonies, they add height and structure without casting shade.

Which plants are best kept away from peonies

However attractive they may look in catalogues, very tall, spreading ornamental grasses planted directly next to peonies can quickly cause trouble. They take away light, crowd the root zone and retain considerable moisture around the foliage.

Species that prefer permanently wet, heavy ground are not a good pairing either. They keep the soil damp for longer and create conditions in which fungal diseases can thrive. 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	Deep-rooted shrubs immediately beside them
Lavender, allium, bearded iris, daylilies	Shallow-planted, aggressively creeping ground cover

Practical tips: planning a low-maintenance peony border

In practice, it works well to treat peonies as the clear stars of the display. First decide where they will sit in the border, then plan the surrounding planting in rings. Keep the soil around the root area largely clear, or plant it only with very low, open companions.

The next ring can consist of lady’s mantle or other low-growing perennials. Around the outside, add a band of lavender, allium or other fragrant protective plants. Hydrangeas and taller structural plants can be positioned behind this, or offset just behind it.

Anyone just starting with peonies should take care not to plant them too deeply. The perennial’s “eyes” – its emerging buds – should ideally sit only a few centimetres beneath the soil surface. If they are deeper, flowering may fail despite the best possible neighbours.

How the right mix pays off over time

A well-planned peony border develops a stable rhythm over the years. The perennials gradually grow together without crowding one another. Pest insects find fewer opportunities because fragrant plants disrupt them, while good airflow is maintained throughout the planting.

Choosing appropriate planting partners means far less intervention is needed: 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 iris, then peonies, followed by daylilies, hydrangeas and the lasting fragrant ribbon of lavender.

When creating new combinations, it is worth considering colours 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 tones. By deliberately placing a few islands of allium and lady’s mantle, you can create a border with simple means in which every peony flower resembles a small painting.