How to grow herbaceous and intersectional peonies

Choosing Herbaceous and Intersectional peonies

Herbaceous and Intersectional peonies are large herbaceous perennials with attractive foliage and large bowl-shaped flowers. Choose a peony based on flower colour and shape. Colours range from white through pink to dark red and yellow. Intersectional peonies also include plants with more unusual apricot and purple shades. The bowl-shaped flowers can be very simple with a single arrangement of petals through to fully-double blousy blooms, including the following forms:

• Single – mostly cup-shaped with 1 or 2 rows of large incurving petals and a large central boss of fluffy yellow stamens
• Semi-double – these have a similar appearance to single peonies but with 2 or 3 rows of petals
• Double – large, rounded flowers with petals that are narrower, overlapping and often ruffled. They fill the centres so you can hardly see the stamens
• Anemone-form – single or semi-double blooms where the central stamens are replaced by narrow rippled petal-like flower structures

Buying Herbaceous and Intersectional peonies

The widest range is available from specialist nurseries often as bare-rooted divisions in late autumn. Plants are also sold in pots ready for planting from late spring to early summer from garden centres.

To track down specific ones you can use our the RHS Find a Plant tool.

When to plant

• Plants sold in pots are best planted in late spring
• Bare-rooted divisions are best planted in late autumn

Where to plant

Try to plant peonies in full sun and a fertile soil, which has been improved by digging in garden compost or well-rotted manure. They will grow well in a range of soils, including clay, as long as it does not get waterlogged in winter and dry out in summer. They are fully hardy so don’t need any winter protection.

We have put together a guide to help you identify your soil type.

Peonies are large plants and need about a square metre (yard) of space without competition from other garden plants in order to thrive.

These peonies are easy to plant and it takes just a few minutes. They are planted in the same way as other herbaceous perennials, but it’s important not too plant too deeply as this may decrease flowering.

• Space plants about 1m (3¼ft) apart depending on their ultimate height and spread
• Dig a planting hole the same depth as the root ball or division and twice as wide
• Draw back the soil with a spade and firm gently around the plant by pressing with your heal of your boot
• Ensure the bright red buds are covered with no more than 2.5cm (1in) of soil as deep planting reduces flowering
• Water in to settle the soil and continue watering regularly, especially in dry weather, during the first summer
• Mulch with well-rotted organic matter to conserve moisture

Watering

Water regularly in dry spells during the first year to aid establishment, especially if planted in spring or summer. Established peonies are deep-rooted and after the first year should not need routine watering.

Feeding

To promote growth and flowers, apply a general-purpose fertiliser, such as Growmore, each year in spring at 70gm per sq m (2oz per sq yd). Then mulch with a layer of garden compost or well-rotted manure to conserve moisture and suppress weeds, but avoid covering the centre of the plant as this could damage the buds.

Staking

Many peonies have very large flower heads so it’s useful to support the stems by staking.

Deadheading

Dead flowers can be removed after flowering using secateurs as most tree peonies are hybrids and often do not set viable seed. Any seed set would, in any case, not breed true and the resulting seedlings would have different flower colours.

Overwintering

Peonies are fully hardy. The foliage dies back in late autumn and the plants remain dormant until spring.

Caring for older plants

Peonies are very long lived and steadily make large clumps. If flowering declines, rejuvenate plants by lifting and dividing in late autumn.

Most commonly grown peonies are hybrids and do not breed true from seed. For this reason they are usually increased by division.

It is best to leave a clump undisturbed until flowering starts to decline. At this point new plants can be produced by division in late autumn.

• Peonies should be divided in the autumn
• Remove the foliage and lift the clump with as many roots intact as possible with a spade
• Gently remove or wash off the soil to expose the roots and growth buds
• Using a sharp knife, remove sections of the crown each with at least three dormant growth buds and some roots attached
• Replant with the buds 2.5cm (1in) below soil level

Plants grown from divisions will be identical to the parent plant and should flower two years after dividing.

Plants of wild species can be propagated from seed as can hybrids but the latter will not breed true (the flower colour and foliage can be different).

• Collect the ripe seed once the seed pods begin to split in late summer and autumn. The viable seed is black. Red seed will not have been fertilised and will not germinate so can be discarded
• Soon after collecting the seed, sow the seed 2.5cm (1in) deep in containers filled with John Innes seed compost Cover the compost  with a light covering of grit and place in a cold frame or sheltered spot outdoors, such as at the base of a house wall
• Make sure that the compost does not dry out in summer and protect from rodents
• Peony seeds need to be exposed to two chilling periods with a warm spell between them. The seeds are doubly dormant; this means the root emerges the next spring after the first chilling period (winter), but the stem and leaves only appear after the second winter
• The seedlings can take up to five years to reach flowering size

In suitable conditions, peonies are generally trouble-free. However, here are a few things you might come across:

• Deep planting and a shady position may result in a lack of flowers. In autumn move the plant to a more suitable position and/or replant shallower (so no more than 2.5cm (1in) of soil over the top of the buds). If moved, it can take a year or two to start flowering again
• Established plants are drought tolerant but prolonged periods of drought in spring can cause poor flower bud development and/or the buds failing to open. Mulch around the base of the plant and water during prolonged periods of dry weather
• Peony wilt (grey mould) that causes wilting and dieback of the foliage as well as buds and flowers is the only serious disease
• Peony blotch (Septoria paeoniae) causes grey-brown spotting with red margins on the foliage, but is not a serious problem
• Ants may be found on flower buds, but they do not cause any damage