How to grow tree peonies

Choosing a peony

Tree peonies have attractive foliage and large bowl-shaped flowers. Gardeners usually choose a tree peony based on flower colour and shape. Colours range from white through pink to dark red and purple; yellows are available too, along with the more unusual apricot shades. The bowl-shaped flowers can be very simple with a single arrangement of petals through to fully-double, blousy blooms. The shapes to choose between are:

Single – mostly cup-shaped with 1 or 2 rows of large incurving petals and a large central boss of fluffy gold stamens

Semi-double – these are like single peonies but with 2 or 3 rows of petals

Double – large, rounded flowers with narrower, overlapping, ruffled petals that fill the centres so the stamens can barely be seen

Buying tree peonies

The widest range is available from specialist nurseries often sold as bare-rooted divisions in late autumn. A small selection 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 the RHS Find a Plant tool.

Buying plants by mail order

Buying plants by mail order

The Hardy Plant Society Peony Group

The Hardy Plant Society Peony Group

When to plant

Tree peonies are best planted in autumn, but winter or early spring planting is also suitable. Avoid planting in late spring and in summer as plants will not establish well in hot, dry conditions.

Where to plant

• Plant in a sunny or lightly-shaded position
• Tree peonies are very hardy, but the foliage and flower buds can be damaged by late frosts so avoid frost pockets
• Choose a sheltered position to prevent damage to flowers and foliage by strong winds
• Tree peonies prefer neutral, humus–rich, well-drained soils, but they will tolerate slightly acid or slightly alkaline soils. It’s possible to improve most soils enough by digging in organic matter, such as garden compost or well-rotted manure, but those which are very acidic or alkaline can remain unsuitable

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

How to plant

• Tree peonies need a little extra care when planting.  Most offered for sale are grafted on herbaceous peony rootstock. Look for the graft union (visible as a slight bulge) close to the base of stem. When planting, the graft union should be about 15cm (6in) below the soil level. Deep planting encourages the grafted plant to form its own roots
• Water in to settle the soil and continue watering regularly, especially in dry weather, during the first summer
• Mulch with organic matter, such as garden compost or well-rotted manure, to conserve moisture. Just avoid piling up mulch against stems as they may rot.

Watering

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

Feeding

To promote good growth and flowering, apply a general-purpose fertiliser, such as Growmore, in each spring at 70gm per sq m (2oz per sq yd). Then mulch with a 10cm (4in) layer of garden compost or well-rotted manure to conserve moisture and suppress weeds, but avoid piling up mulch against stems as they may rot.

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

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

Caring for older plants

Tree peonies are very long lived and most slowly develop into larger clumps. The small-flowered Paeonia delavayi (both red and yellow forms), however, are quite vigorous and stems may need thinning (see Pruning tree peonies).

Tree peonies require minimal pruning. Just remove flowered shoots, cutting them off just above the new growth on the stem in summer; or in the autumn after the seeds are collected if this is desired.

Remove any dead shoots in late winter, cutting back to a healthy bud.

Stems may become leggy over many years. Cut them back by a third in the autumn after leaf-fall to encourage bushier growth.

Tree peonies such as Paeonia delavayi f. lutea and P. delavayi tend to produce more vigorous, upright stems. Removal of a proportion of the oldest stems at ground level in autumn helps to control the size once the plants become established (i.e. they are flowering freely each spring).

Growing from seed

Species such as Paeonia delavayi can be grown from seed as can hybrids, but the latter will not breed true. You might get some interesting new hybrids but, in truth, they are often not as good as their named variety (cultivar) parent. It can still be interesting to try growing from seed, however, and occasionally you will see a self-sown seedling that you might like to grow on.

• 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

Other propagation options

Layering is relatively straightforward if a flexible stem can be bent over. It usually takes two to three years before the stem will produce sufficient independent root system to be separated from the parent plant.

Most tree peonies are commercially propagated by grafting, but this is not a technique commonly used by home gardeners as it takes quite a bit of practice to get good success rates.

Cuttings generally root poorly so are not a great option.

• Poor flowering – Tree peonies can take up to four years to settle in and flower, even when a plant may have been bought in bloom. Tree peonies planted in a shady position tend to flower less profusely. Cut overhanging branches to allow more light to reach the plant or consider moving it. Established plants are drought tolerant, but prolonged periods of drought may affect flowering the following season. Mulch around the base of the plant and water during prolonged periods of dry weather
• Frost damage – emerging foliage and flower buds can be damaged by late frosts. Affected leaves and buds may blacken and fail to open. Protect with fleece during cold nights
• Suckering – shallow planting can encourage suckering of the rootstock. The rootstock is usually P. lactiflora which has shiny reddish shoots, whilst the shoots of tree peonies have a dull light red colour. If not sure, investigate if the shoots originate from below the graft union (visible as a slight bulge close to the base of stem). Remove the suckers as soon as they appear at the point of origin with a sharp knife
• Peony wilt (grey mould) that causes wilting and dieback of the foliage, as well as buds and flowers, is the only serious disease