How to grow Tree Peonies
You can grow Tree Peonies in the ground, or in a container, they are remarkably drought tolerant and with a little soil preparation are very easy care. As long as they get good water from winter through spring they will thrive.
Although Tree Peonies do not like hot dry conditions, they do grow well in Australia, especially in the cooler temperate areas.
Most are hybrids of Paeonia suffruticosa or Peony rockii and you will read that they are drought tolerant. Although they can cope with a dry summer they do require good moisture from mid winter to early summer, and a cool root run through summer.
So why are they regarded as drought tolerant, simply because they do not require a lot of water during summer, they do need some moisture and cool soil to do well.
And what does Paeonia suffruticosa mean in botanical terms ? Simply that it is a peony and that it has a suffrutescent stem, a woody base (like a tree) that does not die back during dormancy, it is only the very top that partly dies back.
Pictured right is a young plant showing clearly the new shoots and the single stem that will need to pruned back.
Tree peonies – the secrets to growing them
Lots of articles are published saying how difficult these plants are to grow, if you live in the right climate, the cool temperate zones they are in fact remarkably easy. We grow them with very little fuss and here are the three ‘not so secret’ factors.
- Sun in winter and spring, but afternoon shade
- Humus rich deep soil that stays moist
Many gardeners look at tree peonies and on seeing the delicate flowers decide to plant them in the shade, invariably this leads to poor flowering. So full sun in winter and spring.
Soil needs to be humus rich, well drained but moist. It is a big mistake to think that because tree peonies are touted as drought tolerant that they require little to no water. In recent drought years with little winter rain and not much in spring a few gardeners lost well established plants. The cold of winter activated the growth pattern, however without water plants died.
A friend of ours grows wonderful peonies, they grow between the brick house and a concrete path. Both the house foundations and the path contain lime which leaches into the soil and peonies love lime. So when planting dig in lots of lime.
Tree Peonies – how to plant them
Having chose a suitable position and amended the soil with well rotted compost, ensure that drainage is excellent, peonies do not like wet feet.
If you have a potted plant make sure that it is well established with a good root system, some nurseries sell newly potted, rather small poorly rooted plants in pots, these should be left in the container for a year to avoid transplant shock.
- Dig over an area around 2 – 3 times the size of the pot and around .5m deep.
- Dig in some well rotted compost and maybe some aged animal manure.
- Dig in around 3 – 4 kg of dolomite lime.
You are now ready to plant at the same depth that the potted plant was at. If the plant is newly potted, simply plant the whole pot. You can remove it from the pot the next autumn and plant it in the ground.
Water in well and your tree peonies are ready to go.
- Use a low nitrogen fertilizer in autumn and again in late spring.
- Mulch lightly in late spring to help retain some moisture over summer.
- Only water in summer in very dry spells.
- Once the foliage begins to die back in late summer clean up fallen leaves to help prevent disease.
Tree peonies – how to prune
Tree peonies require little to no pruning, only dead or damaged wood need to be removed. Some gardeners like to open the centre of the plant to promote good air flow. A small dead section high on the plant is common, tree peonies tend to shoot from a little lower down, so you can prune this back to a new bud.
Every second year apply additional lime, around .5kg
Tree Peony – problems
- Pale foliage turning light green to yellow. Usually an indication of chlorosis and this is partly caused by the addition of lime. The lime is needed so add some iron chelate
- Different foliage appearing. Tree peony foliage is lobed with a pink tinge to it. As tree peonies are grafted they are actally grown on herbaceaus peony rootstock you will sometimes get shoots from the rootstock these can simply be pulled away or cut beneath the ground.
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Growing in containers
Although not ideal, tree peonies are good candidates for growing in containers if needed. Use a largish container at least 30 cm across. A free draining potting mix and remember that extra lime.
They are easy to move, best in autumn, take as much of the roots system as possible and remember to prepare the new position with compost and lime first. Most tree peonies are grafted, they are grown on a stronger rootstock, so ensure that the graft is is around 10cm below the soil level, this will ensure good new shoots.