The launch of a tree peony commemorating reality TV star Jade Goody, who died last month, is likely to revive consumer interest in these woody-stemmed perennial shrubs, which are grown for their bold flowers. There are two different types - the large-flowered varieties, which are derived from P. suffruticosa, and the smaller-flowered types, which are derived from P. delavayi Award of Garden Merit.
The strange, voluptuous, blousy flowers bloom in April and May, and are ideal for a mixed herbaceous border as their colourful blooms can brighten up a dull corner of the garden. Some varieties are scented. The colours are similar to those of the herbaceous peony, including white, pink and red, but many varieties produce true yellow flowers.
Flower types range from the large, yellow double flowers of P. x lemoinei 'Souvenir de Maxime Cornu' to the smaller, cup-shaped single flowers of P. lutea.
Bushes have an upright habit and can become leggy after some years, so older stems need to be pruned to the ground in spring. Flowered shoots need to be pruned back to new growth in autumn and flowers should be deadheaded unless seed is required.
The plants can be grown from seed but take about seven years to flower. Seeds of all peonies are double-dormant and need two winters of chilling. The more vigorous varieties can be propagated by division. Grafted plants should be planted so that the graft union is at least 10cm below the soil surface. Hard pruning can encourage a plant to send out suckers and so create a denser bush.
Tree peonies prefer a sheltered site as young foliage can be damaged by sun following frost. They are hardy, however, and not susceptible to pests and diseases, although they can be vulnerable to peony wilt (Botrytis paeoniae), especially during wet springs.
A mature plant can grow to 2m or more in height and can have 100 flowers on one bush. Plant in fertile, well-drained soil in a sheltered spot that gets some sun during the day, away from large trees. In spring, apply a general-purpose fertiliser and mulch with well-rotted organic matter.
There are more than 1,000 peony varieties. The tree-like peonies are shrubs that are rarer than ordinary peonies but are becoming increasingly available from China, Japan and the US.
WHAT THE SPECIALISTS SAY
Paul Hansord, young plants manager, Thompson & Morgan "We sell a wide range. We're bringing P. rockii - the straightforward variety in different colours - through to the trade. We're creating a demand for it.
"We have good-quality plants at a good price. I've been out to Mongolia to select them and they are fantastic quality there. It's not easy to source good ones. They're very slow to grow and when fashion comes around to tree peonies you need five or six years to get a quality plant grown. It's a long and expensive process."
Billy Carruthers, owner, Binny Plants, West Lothian "There was a mad rush on tree peonies a few years ago. It's difficult for us to tell if they are becoming more popular because our sales go up more and more as we build up as a business specialising in peonies. We now have over 300 varieties in stock, including 30-40 tree peonies.
"We don't import from China. We get them from the US, where we know they're properly named. They're expensive at £20 to £75. We don't do Japanese hybrids in Scotland. Chinese hybrids do better here. New-generation tree peonies include hybridised P. lutea and P. delavayi Award of Garden Merit (AGM). The flowers are not as big and blousy as Chinese plants, but they are hardier.
"Best-sellers are P. delavayi AGM, P. lutea, P. 'Anna Marie', P. 'Black Panther', P. 'Ezra Pound', P. suffruticosa 'Hana-kisoi' and P. 'Joseph Rock', which is expensive at £75, but is the ultimate peony for a lot of people. It's difficult to get the true plant but we do sell it.
"There's no real problem with pests and diseases, just the usual things like peony wilt. Good housekeeping is the best way to keep that under control - keep air circulating and remove decaying material. They can be sprayed with Cheshunt Compound early in the season."
Pauline Brown, proprietor, Buckingham Nurseries & Garden Centre "We usually have at least five varieties. They sell very well because it is becoming more obvious that they survive well in this area. In the past it was always thought they were too tender, but now we are seeing them do extremely well.
"They need fleecing in spring because of the chance of frost. We fleece when there is any frost warning. There are no pest and disease problems as far as I know.
"We sell the standard P. suffruticosa in one-litre pots at £8.99 in different colours. We sell named varieties in four-litre pots at £19.55, which seems a lot but they are very popular. The big four-litre varieties come with a good picture.
"Least popular is the white, although it is my favourite, while the pinks and reds are equally popular and sell as quickly as each other. My own plant in my garden had a bit of dieback during the worst weather this spring but is already bouncing back with new shoots."
Karl Cooper, plant manager, Millbrook Garden Company "They are something we would stock if we could get hold of decent plants. They have gone out of fashion a little bit. We don't get a huge demand for them - there's more demand for the traditional type.
"We have some we overwintered at our branch in Gravesend, Kent. We sell Japanese varieties, which often have unpronounceable names. They're the only varieties that seem to be available at the moment. Nurseries find them difficult to produce - they get a lot of losses."
SPECIES AND CULTIVARS
P. 'Argosy' is a compact, deciduous shrub with mid-green leaves that are deeply divided into pointed lobes. It bears cup-shaped, lemon-yellow single flowers with a crimson base.
P. delavayi Award of Garden Merit (AGM) has pinnate, dark green leaves and bears cup-shaped, dark red flowers that are 10cm across.
P. delavayi var. delavayi f. lutea has vivid, single, cup-shaped yellow flowers that grow to 6cm across. The species has dark green leaves, which are blue-green underneath. Hybrids of P. lutea include the vigorous, fresh yellow P. ludlowii AGM.
P. 'Kronos' is an upright, sparsely branched tree peony with red-tinged shoots and red-stalked, dark green leaves. Blue-tinged, dark-red semi-double flowers are 15cm across.
P. x lemoinei is an upright to spreading, sparsely branched cross of P. lutea and P. suffruticosa, with dark green leaves and cup-shaped single to double flowers that are 15-20cm across. They are white to yellow, often with orange, red or pink marks. P. x lemoinei 'High Noon' is a frilly cultivar.
P. x lemoinei 'L'Esperance' has mid-green leaves with pointed lobes. It bears cup-shaped, primrose-yellow single flowers with a red base. The flowers are 20cm wide and have red filaments and yellow anthers.
P. x lemoinei 'Souvenir de Maxime Cornu' has yellow, double flowers that are fragrant. The blooms are 20cm wide and have ruffled petal margins that are reddish orange.
P. 'Madame Louis Henri' bears orange, semi-double flowers that are 17cm across. The plant grows to a height of 2m and 1.5m wide.
P. suffruticosa has cup/bowl-shaped white, pink, red or purple flowers, 15-30cm across. Hybrids of P. suffruticosa are available in all shades of pink from the delicate, shell-tinged 'Haru-no-akebono' to the rich purple 'Cardinal Vaughan'. P. rockii (also known as P. suffruticosa subsp. rockii and P. 'Joseph Rock') has a blackcurrant blotch at the base of pure white petals and is one of the most expensive varieties.
P. suffruticosa 'Jade' is a new introduction this year, initially being sold in limited quantities for charity. It has large, green-yellow double blooms and pale green foliage, and grows to 1.5m.