Herbaceous peonies provide invaluable colour to borders and cut flower material in late spring and early summer. Their large, often double flowers in whites, pinks and reds add an element of romance and glamour to any garden.
Herbaceous peonies differ from woody-stemmed tree peonies in that they die back to ground level every winter. The successful crossing of tree and herbaceous peonies by plant breeders produced intersectional (Itoh) hybrids. Lately they are more readily available, but still expensive.
Unjustly, peonies are often considered difficult to grow, but with some basic care they can provide colour and enjoyment for many years;
- Ideally plant in full sun, though a few will tolerate light shade
- Most prefer neutral to slightly alkaline soils; some such as P. anomala are best planted in slightly acid soil
- Good drainage is essential
- Peonies are relatively drought tolerant when established though flowering may be impaired during particularly dry spells at the time of flower bud development
- Feed with a balanced general, fertiliser such as Growmore in the spring at 70g per sq m (2oz per sq yd), but avoid over-feeding with high nitrogen fertilisers. Plants grown on rich soils generally require little feeding
- To conserve moisture and suppress weeds, mulch around the crown with 5-7.5cm (2-3in) organic matter such as composted bark, garden compost or well-rotted manure. Avoid covering the crown itself
- The flower stems may not be strong enough to keep the often heavy flamboyant flowers upright and staking is often required
- It is generally best to cut the foliage to ground level as it dies back in the autumn to reduce risk of peony wilt
Herbaceous peonies have thick, tuberous roots and are sold as either bare-root or container-grown plants. Bare-root plants usually have at least three or four growth buds and produce flowering plants quickly, often within a season or two of planting. Container-grown plants often have fewer (two to three) buds and can take longer to establish.
- Ideally plant in the autumn. Alternatively, plant in early spring
- Prepare the planting area by incorporating organic matter such as garden compost or well-rotted manure
- On poor soil apply a general fertiliser such as Growmore as at 70g per sq m (2oz per sq yd)
- Avoid deep planting; make sure that the top of the crown is 5cm (2in) below the soil level
- If planting actively-growing plants, it is generally best to plant at the same soil level as in the pot
- Water regularly when rain is lacking during the first year to aid establishment, especially if planted in spring or later in the season
Herbaceous peonies are not well-suited for long term container cultivation. If necessary, for example when moving house, lift the plant preferably in the autumn. Otherwise, do it in early spring. Use soil-based potting compost such as John Innes No 3. Do not let the compost dry out. Plant it out into the final position as soon as possible.
Contrary to popular belief, herbaceous peonies can be successfully moved. This should be done in the autumn. Try to cause as little disturbance to the root system as possible. This can prove challenging as established clumps have deep tuberous root systems and the roots are brittle. Avoid replanting too deeply as this may adversely affect flowering. It can take a couple of years for the plant to settle.
It is easiest to propagate herbaceous peonies from division, but seed is also possible.
- Species peonies are self-fertile and, in the absence of other peony species, will produce seed true to type. They will, however, easily cross with other peonies and so unless the species is isolated, hybrids may well occur
- Cultivars and hybrids, on the other hand, may not produce seed, or where they do, they are unlikely to produce offspring true to the parent plant
- 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 after the first chilling period but the stem and leaves only appear after the second winter
- In late summer or autumn, sow fresh ripe seed 2.5cm (1in) deep in containers filled with soil-based seed compost
- Bought seed is generally dry and not fresh, so germination can be disappointing
- Cover the compost lightly with grit and leave outdoors
- Make sure that the compost does not dry out in summer and protect from rodents
- The seedlings can take up to five years to reach flowering size
- Peonies should be divided in the autumn
- Remove the foliage and lift the clump carefully
- Gently remove or wash off the soil to expose the roots and growth buds
- Using a sharp knife, remove sections of the crown with at least three dormant growth buds each and roots attached
- Replant with the buds 5cm (2in) below ground level
- Species peonies are not as vigorous as cultivars so divisions from them are generally best planted with the buds only 2.5cm (1in) below ground level
Paeonia 'Bowl of Beauty': Cupped, cerise pink flowers with a central mass of cream petaloids, 80-90cm (32in to 3ft) tall.
P. lactiflora 'Sarah Bernhardt' AGM: Fragrant double pink flowers, 90cm (3ft) tall.
P. cambessedesii AGM: Grey-green foliage with purple tinge on the underside, purple-pink flowers, compact species suitable for rock gardens.
P. officinalis 'Rubra Plena' AGM: Large deep crimson red flowers, 75cm (30in), may need staking.
Container-grown plants often are sold with fewer buds and may take longer to become established.
Deep planting and a shady position can account for a lack of flowers. Consider moving the plant to a more suitable position and/or replant shallower. If moved, it can take a year or two to establish in the new position.
Though established plants are drought tolerant, prolonged periods of drought in spring during the flower bud development can be the 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 blight) that causes wilting and dieback of the foliage as well as buds and flowers is the only more troublesome disease.
Herbaceous peonies are prone to peony ringspot virus that causes appearance of characteristic irregular yellowish rings on the foliage. This virus generally does not cause major problem to the infected plant and can be tolerated by domestic gardeners. Sterilise secateurs after pruning to avoid spreading the virus from plant to plant.
Peony blotch (Septoria paeoniae) causes grey-brown spotting with red margins on the foliage, but it is not considered a serious problem. There are no specific sprays for this disease.
Dieback and wilting of the may be caused by verticillium wilt.
Honey fungus can cause the decline and death of peonies.
Leaf discolouration, wilting and eventual death may be sign of a leaf and bud eelworm (nematode) infestation. It is a microscopic pest living in the plants’ tissue. It affects foliage as well as flower buds starting on the lower leaves. Blooms may be distorted and stems could show scaring. There is no cure and plants should be destroyed.
Ants may be found on the buds, but the do not cause any damage and can be tolerated.
The foliage can be damaged by various caterpillar pests. Try checking the plant after dark on mild evenings and remove.