Paeonia Lactiflora and Paeonia Officinalis
Peonies make a resounding splash in the summer border, their large, strikingly coloured flowers and rich veined leaves a head-turning focus of attention. In autumn the herbaceous sorts die down to fleshy crowns with buds which produce new growth the following spring. Other peonies are shrubby, and often go under the grander but visually quite unmerited name of ‘tree peonies’. These have woody stems which remain all winter and form a permanent framework of growth.
Some herbaceous peonies cultivated in gardens are species appearing just as they would in the wild, but most are either hybrids or special selections, often with very large double or semi-double flowers. Among the best species, all with single flowers, are Paeonia peregrina, often called Paeonia lobata, with scarlet, goblet-shaped flowers; Paeonia mlokosewitschii, with very large primrose yellow flowers; Paeonia obovata, with white or magenta flowers, and Paeonia tenuifolia, with very finely divided leaves and light crimson flowers.
The garden varieties fall into two main groups, one derived largely from Paeonia lactiflora and known as the Chinese peonies, the other from Paeonia officinalis and often referred to as the Cottage Garden peonies. The Chinese peonies have the greatest range of colour and flower forms, white, pink, lilac, rose, carmine and crimson, single, semi-double, fully-double and anemone-centred. Most are also scented and their peak flowering season is in June. The Cottage Garden peonies are all very fully double, white, pink or crimson and not scented. They flower in May.
All herbaceous peonies like rather richand a sunny or partly shaded position. They dislike being disturbed, and if grown in mixed borders they should be so placed that they can be left alone when other plants are lifted and divided. Increase is by division in spring or autumn but this usually stops plants flowering for a year or so until they have re-established themselves. The species can all be increased by seed sown outdoors or under glass in April-May or as soon as ripe, but it may be a few years before are large enough to flower.
Tree peonies are also divided into species and hybrids, the former with single flowers, the latter usually double. The best species are Paeonia delavayi, a big bush with rather small deep crimson flowers; Paeonia lutea, even bigger in growth with yellow flowers which are a little larger in the variety `Ludlowii’, and Paeonia suffruticosa, usually smaller in growth but with much larger white, pink or magenta flowers often with blotches of darker colour at the centre of the bloom. The hybrid tree peonies are derived mainly from Paeonia suffruticosa with some interbreeding with Paeonia lutea to introduce yellow. This gives a very wide colour range including white, pink, carmine, crimson, orange and yellow often with two colours combined. The flowers are sometimes so immense that they hang downwards under their own weight and require some support.
These hybrid tree peonies are a little more difficult to grow than the species. Less hardy, more susceptible to spring frosts which can damage the young growths, they particularly need good rich soil with plenty of moisture in spring and summer but reasonably good drainage in winter.
The species are easily raised from seed and often produce numbers of self-sown seedlings. The big double tree peonies produce little or no seed which would not, in any case, produce flowers of identical character and so they are either layered in spring or, less satisfactorily, grafted on to herbaceous rootstocks.