Peonies: the best companion plants for spectacular blooms

Anyone who loves peonies can make their floral display positively burst into life with the right bed companions – provided a few basic principles are in place.

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

What peonies need before you pair them with other plants

Peonies are among the garden’s longest-lived 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 that still provides at least four to five hours of sunshine each day.

Their soil should be deep, rich in humus and free-draining. Peonies strongly dislike waterlogged ground during winter, as their roots can quickly rot. Fierce root competition from particularly vigorous neighbouring plants is equally unsuitable.

If peonies are hemmed in too closely, fungal diseases and disappointing flowering are likely – generous airflow 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 in the foliage, and the result is an ideal breeding ground for grey mould and other fungi. Buds may then collapse, flowers become misshapen or fail to open altogether.

Three straightforward rules will help with any planting plan around peonies:

• Choose only perennials that enjoy sun and a well-drained, reasonably nutrient-rich soil.
• Avoid placing substantially taller plants directly in front, where they will shade the peonies.
• Leave a small “pool of light” around each plant so that air can move freely.

Alchemilla and other ground cover plants that make peonies shine

Once the basic conditions are right, it is time to choose the supporting plants. Lady’s mantle (Alchemilla mollis) is an especially good match. It creates a loose carpet of soft, pleated foliage, topped with airy clouds of yellowish-green flowers.

This restrained colour has a striking effect: it makes the delicate pink and white shades of peonies appear much more vivid without stealing the spotlight. The pairing works just as well in a flower arrangement as it does in a perennial border.

Bellflowers as graceful companions

Compact types of bellflower also create a very harmonious combination. Many varieties produce delicate white, blue or violet blooms in early summer. They provide a light, romantic setting while avoiding competition with the peonies’ root mass.

One point deserves attention, however: bellflowers can sometimes attract more insect pests. If you combine them, do not plant too densely and include a few “protective plants” nearby to deter unwelcome visitors.

Hydrangeas at the back: a backdrop for large peony flowers

Hydrangeas are excellent for adding structure at the rear of a border. Their large rounded flower heads echo the circular shape of peony blooms without overwhelming them. Set at a little distance, they form a calm background.

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

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

• Bearded iris: usually flowers shortly before peonies, opening the season for them.
• Allium: ornamental onions add architectural spherical flowers among the perennials from late spring.
• Daylilies: take over in high summer, bringing colour once the peony flowers have finished.

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

Lavender as a fragrant protective hedge around peonies

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

Its essential oils deter many troublesome visitors: mosquitoes, flies and some beetles, while deer and rabbits often avoid areas edged with strongly scented rows of lavender. If your peonies grow in border beds, position lavender right along this outer edge.

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

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

Which plants should not be placed at the feet of peonies

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

Plants that prefer permanently wet, heavy ground are also a poor match. 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 companions	Better avoided
Lady’s mantle	Very tall ornamental grasses
Bellflowers (compact varieties)	Perennials for permanently wet soils
Hydrangeas at the back	Deep-rooted woody plants immediately alongside
Lavender, allium, bearded iris, daylilies	Shallow-planted, strongly creeping ground cover plants

Practical tips: planning a low-maintenance peony border

In practical terms, it works best to treat peonies as the undisputed stars of the border. First decide where they will sit, then plan the surrounding planting in rings. Keep the ground around the root area largely clear, or use only very low, open-textured companions.

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

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

How the right mix pays off over time

A carefully planned peony border develops a stable rhythm over the years. The perennials gradually grow together without crowding one another. Insect pests find fewer opportunities because fragrant plants disrupt them and air circulates well through the planting.

Choosing suitable companions also means much less intervention: fewer supports, less summer cutting back and fewer fungal treatments. At the same time, the garden remains lively from late April far into summer – first with irises, then peonies, followed by daylilies, hydrangeas and the lasting scented ribbon of lavender.

When trying new combinations, consider colours and flowering periods. Pastel-coloured peonies can carry strong blue and violet partners, while vivid pink or red varieties look calmer alongside soft yellow and cream shades. By deliberately placing a few islands of alliums and lady’s mantle, you can create a border with simple means that makes every peony flower look like a small painting.