Peonies
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Peonies are among the most beautiful of the herbaceous perennials. They have colour in abundance and many also have fragrant flowers and attractive foliage, and they’re very easy to cultivate provided your climate is suitable. Peonies are among the few perennials that rarely (often never) need to be lifted and divided. Indeed, they often do better if left alone.
Peonies need winter chilling to enable proper bud formation and development. Many North Island coastal areas are not quite cold enough in winter to chill them adequately, with the result that the flower display tends to sparse and undersized. Also, there may be problems with peonies not dieing back properly in autumn, which stresses the plants as they really do need a dormant period.
Apart from those possible problems, which you really can’t do anything about save moving, peonies are easy to grow. The main consideration is getting the soil conditions right at planting time. In some climates, such as part of Canterbury and Marlborough where the nor’wester howls, peony buds are vulnerable to hot, dry winds burning the outer petals of the flowers before they open. Very late frosts can also cause a similar effect and may damage soft new growth.
Soil preparation and planting
Peonies demand a rich, well-drained, humus filled soil and ample moisture when actively growing. They tolerate a wide range of soil types but do best with a near-neutral pH of around 6.5–7.5. They are very hardy and are well able to withstand the coldest New Zealand conditions — in season.
The best time to plant peonies in autumn and winter, in other words when they are near-dormant. As stated earlier, peonies are long-term plants that are seldom lifted, so take plenty of time to prepare the soil when planting — it’s your best way to ensure good results. Work in as much compost as you can and add a little blood and bone or bonemeal as a quick boost fertiliser. If you suspect that your compost or soil may be quite acid (compost made from leaf mould or with lawn clippings often is), add some Dolomite lime, but don’t overdo it: we want neutral, not alkaline, soil.
When you buy roots from a nursery or garden centre make sure they are reasonably large — with 3–5 reddish-pink buds or ‘eyes — and that they are free from rots or any signs of fungal diseases. Smaller divisions will survive, but they may take up to five years to bloom regularly. While you should return damaged roots if you find any among bought stock, if you have any damaged material of your own, a tidy up with a sharp knife followed by dusting with flowers of sulphur or fungicide powder should stop any rot.
Dig a reasonably deep hole, say 30–45 cm, backfill it with a compost and soil mixture, add your powdered fertilisers and stir them in. Then place the peony root, eyes up, at a level that will be about 3–5 cm below the soil surface. Peonies planted too deeply can have their foliage damaged as it pushes up through the soil and may fail to flower well. Firm the soil in around the roots to eliminate air pockets and then top off with more of the soil and compost mixture. Allow at least a metre between clumps so that the plants have plenty of room to grow and you won’t have to lift them in the near future.
In areas where the soil freezes to more than a few centimetres, it is often a good idea to plant early or delay planting until the worst frosts are over. If you plant in mid winter you may find that the roots are raised out of the soil by frost heaving.
Peonies will grow in sun or part shade, though the flower quality is usually best on plants that are in the sun for most of the day. The stems are also more compact and sturdier on sun-grown plants, which enables them to better support the heavy flowers.
Routine care and maintenance
There is little you can do to modify the soil once your peonies are growing well, so feed regularly to keep them growingsteadily — a starving peony will be a poor-performing peony.
As with most plants, regular light mulching is one the best ways to apply fertilisers. Use a good compost and incorporate a handful or two of blood and bone. Don’t put the mulch on too deeply — a couple of centimetres is fine — and don’t use high-nitrogen fertilisers or you may get masses of lush foliage but only a few weak-stemmed flowers. If you are using chemical fertilisers or can get an analysis of your organic feeds, look for a ratio of around 4-12-4. If your peony stems look weak and spindly, consider a 3-12-12 blend for a potassium boost.
Peony enthusiasts often disbud their plants to produce larger flowers. Leaving the central bud and removing the lateral buds when roughly pea-sized will maximise the size of the remaining flower. However, home gardeners may prefer more small flowers to a few large ones. Removing the seed heads after flowering is advisable to ensure good flowering in the following season.
Peonies are also excellent cut flowers, and if cut just prior to opening they will last for a considerable time.
After the growing season, cut back the foliage to within about 8 cm of the soil surface. If there have been any disease problems destroy the foliage, otherwise it can go in the compost.
Pests and diseases
Peonies in New Zealand are remarkably free of pests and diseases. The most common problems are soft rots affecting roots that have been recently divided or stored too long. These problems are best controlled at planting time by discarding the worst affected roots and treating the remainder with fungicides.
Occasionally you may see the effects of a form of Botrytis unique to peonies, Botrytis paeoniae, which cause the buds to rot and the foliage to blacken. Systemic fungicides can control the problem but you should also look at the growing conditions: are the plants overcrowded, is the soil well-drained or has the season been particularly wet. Any of these conditions can cause ideal conditions for botrytis to develop and spread.
If the soil is inclined to develop a hard crust, the stems can be damaged as the push through in spring. Regular mulching can eliminate this problem. Damaged stems can develop distorted growth and become unsightly, they may also fail to flower, but more importantly they are more likely to become diseased.
In most areas pest damage is rare or minor and there is nothing that is unique to peonies, just the usual caterpillars, beetle larvae and the like — generally nothing to worry too much about.
Propagation
Named peony clones are usually propagated by division, which is difficult as the plants have very strong woody roots that may have to be sawn up rather than simply divided. Also, one root does not yield many divisions. This explains why peonies are among the more expensive perennials. Seedling peonies are relatively cheap but of course you don’t know exactly what the quality of the flower will be like.
Freshly divided peonies often take some time to settle down into a pattern of steady growth and regular flowering. You may get the odd bloom straight away, but don’t be surprised if you see nothing for the first two seasons after division.
Herbaceous peony hybrids
Peonies are classified according to flower type. There are three main types and two sub-types.
* Single. The flowers resemble large camellia blooms and have prominent central boss of golden stamens.
* Semi-double. Some of the central stamens become petaloid while others do not, creating a loose, partially petal-filled centre. Anemone-form flowers have their outer stamens transformed into petals to create a ring or second tier of petals in the centre of the flower. Japanese types are similar but it is their central stamens that become petaloid, leaving a ring of stamens around the central petals.
* Double. All the stamens become petaloid to create a very full flower that is usually infertile as a pollen parent.
There are countless cultivars, mostly derived from P. lactiflora, and the following is just a very small selection of the more commonly available.
‘Albert Crousse’. Double. Soft pink.
‘Auguste Dessert’. Japanese style semi-double. Bright pink with lighter edges.
‘Autens’. Double. Red
‘Charlie’s White’. Semi-double. white.
‘Festive Maxima’. Double. White with red flecks. Very fragrant.
‘Inspecteur Lavergne’. Double. Red.
‘Karl Rosenfeld’. Double. Deep pink.
‘Krinkled White’. Single with broad crinkled petals. White.
‘Madame Emile Debatene’. Double. Soft light pink with paler outer edges.
‘Moon River’. Double. Light pink.
‘Mrs Franklin D Roosevelt’. Semi-double to double. Soft pink.
‘Sarah Bernhardt’. Double. Light pink.
‘Shirley Temple’. Double. White to pale pink. Fragrant.
Herbaceous peony species
Occasionally you may see species for sale. They can be very attractive plants, though their flowers are generally of the single type. Look out for the following species, all of which are subtly beautiful without being overtly showy.
P. anomala. Deep pink, loose-petalled flowers. Very narrow leaflets.
P. emodi. White flowers. Narrow leaflets. Early.
P. lactiflora. White flowers. Dark foliage. Double forms are common and gave rise to most of the garden peonies.
P. mascula. Deep pinkish red flowers. Early. There are several subspecies with differing leaflet shapes.
P. mlokosewitschii. Red buds open to pale yellow flowers. Rounded leaflets. Brown seed pods open to reveal black seeds on a red background. Good autumn foliage colour.
P. tenuifolia. Bright red poppy-like flowers. Foliage with very narrow leaflets resembles that of an anemone.
P. veitchii. Mid pink, loose-petalled flowers and narrow, finely divided leaflets.
Peony nurseries and gardens
Take care when buying peonies from garden centres: they are sometimes mislabelled. If possible, buy your plants in flower so that you can be sure of what you are getting. Failing that it is best to buy from a specialist nursery, most of which have a display gardens you can visit.
Copyright Geoff Bryant
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