Treat yourself to a tree peony
You can’t beat them for hardy, long-lived additions to your garden
The term tree peony can be confusing because it seems to describe a plant that grows to the height of a tree, which a tree peony doesn’t.
The main difference between tree peonies and their herbaceous cousins is that the former don’t die back in winter. After the leaves have dropped in late autumn a scaffolding of woody stems remains. For this reason they should more aptly be called shrubby or woody peonies.
The other difference is that the flowers and leaves are much bigger than herbaceous peonies and, until recently, they were the only peonies to produce truly yellow flowers.
Flowering between late May to mid June, all peonies like to be grown in well-drained soil, including clay, in a sunny spot. You can grow them in a pot, providing it is at least 40cm (16in) wide. Replenish the soil in the pot every few years and water the plant frequently early in the growing season. Generally, a lack of water in spring and too little sunlight are the main reasons peonies don’t flower, while too much fertiliser can create lots of leaves and few flowers.
Tree peonies are extremely hardy and long-lived plants. They can be left undisturbed for many years, but the method of planting is important with grafted varieties. Make sure the grafting junction is at least 15cm (6in) below the surface of the soil. This prevents the grafting stock from taking over.
In autumn, cut back the old leaves and prune any dead stems back to a new flower bud. If a stem is too big, or the plant is a funny shape, it can be pruned to a lower bud.
Types of peony
There are three basic types of tree peonies. The most readily available are the substantial Paeonia delavayi types, which are only suitable for bigger gardens. P. delavayi produces small, dark red, single flowers that tend to hide in the leaves. There are two yellow forms comprising P. delavayi lutea, with small, single flowers, and P. ludlowii which has bigger yellow flowers. Raised from seed, they can cross and the resulting blooms may open in beautiful shades of apricot and melon. The most ancient tree peonies are those that come from China. P. rockii is a well-known plant of Chinese origin, but the Chinese have been hybridising tree peonies for centuries. Highly-regarded as garden plants, they were grown in the gardens of emperors and for medicine. The Victorians imported tree peonies from China into Britain, but although they
were never in great demand, the trade stopped with the Cultural Revolution of the 1960s and 70s. With the opening up of China in the late 1990s, more have been coming into Europe. However, as they originate from northern China, which has a more extreme climate than Britain, I’ve found they don’t flourish and often fail to flower in our warm, wet climate. The other drawback is that they hide their beautiful flowers – the blooms often hang downwards because they’re so big and heavy, so you cannot see them too well.
The Japanese tree peony corrects many of these issues. The glamorous flowers are single or semi-double and produced on a graceful, open shrub. They grow no taller than 1.2m (4ft) high, often less, making them suitable for smaller gardens.
There’s one downside and that is they can start into growth much earlier in spring than other peonies. The buds fatten rapidly on warm days, especially in February. This makes them prone to frost damage which causes the flower bud to shrivel and turn brown. So if you want to grow a Japanese tree peony – and these are the unnamed ones you tend to find in garden centres – plant it away from a frost pocket.
Lutea hybrids
The third and most beautiful type, but the rarest, are the tree peonies raised by American botanist and peony expert Professor A. P. Saunders during the middle of the 20th century. These are known as lutea hybrids.
These are crosses between species and named peonies. The resulting plants grow to between 90cm (3ft) and 1.2m (4ft) high, flower during June with blooms that face upwards and come a in range of tones that vary from soft yellow to rich red.
Like almost all tree peonies, lutea hybrids are propagated by grafting – a technique that needs much skill. For this reason many tree peonies are difficult to find. If you do find them, they can be expensive.