Can you prune camellias?
Because I have spent most of my life gardening on non-acid soil I have had to grow camellias and other calcifuges (plants intolerant of high pH) in pots, the idea of having to prune camellias has never really been one that has concerned me. Even with the best will in the world and the most conscientious watering, most camellias, along with rhododendrons and pieris, were doomed to dry out at one point and then die. And if they did survive, there came a time when they were too big and had to be planted out – but where? I remember a huge camellia I bought when I was living with my parents and we put it in a half barrel where it grew well for more than a decade. I am not sure what happened to it but I suspect it was finally planted in the garden which, being clay over chalk at the foot of the North Downs (in SE England) it died an exquisitely painful and lingering demise with early stages of chlorosis, followed by falling, yellow, brown-edged leaves and eventual, merciful death. I feel awful just thinking about it.
But lots of people garden on acid soil, as I do now, and camellias are (relatively) easy. I suffer from wind and moderate exposure – well the garden does, so I can’t take camellias for granted, but there are lots of gardens around where they do well. I have made tentative steps to add camellias and, though they have not surprised me with their vigour, I am finding sheltered places, away from the wet soil they detest (though they do need moisture – just not sodden) and they are getting bigger and have flower buds.
In more favoured spots camellias can become huge and they can be used, very effectively as hedges. So how and when should you prune a camellia?
Remember that camellias flower in spring. Their flower buds form on the new shoots that grow from May to August and then mature into autumn. You can usually tell, by September, which are the fat flower buds and how many blooms you will get the following spring. Growth buds are narrow and pointed and flower buds are much fatter. In fact, drought at this time (August) can cause the flower buds to abort, slowly, so you may need to water a camellia in the ground then if the weather is dry and you certainly must keep plants in pots moist.
So don’t do any pruning from July to April or you will cut off flowers. You can prune immediately after flowering. If your plant is young, as mine are, some pinching is helpful, especially with Williamsii types, such as ‘Donation’ (top photo) which is naturally tall and slightly spindly.
You don’t need any tools, just pinch out the top growing bud from each shoot. Then the two or three buds below will grow and it will become much more bushy. It really helps the shape early on and will not affect flowering – it may actually produce more flowers as there are more shoots.
But if you have a large plant and it needs pruning, you can do this immediately after flowering, so the plant has all season to make new growth to bloom on. You can be quite severe – old stems as thick as your arm will sprout. In the same way you can go over a camellia hedge with hedge-trimmers, if necessary or reduce the height by a metre and the plant will not be harmed.
If you do reduce a 3m high camellia to a 60cm stump, it can be useful to wrap the stumps with hessian and keep that damp for a few weeks. I have done this with camellias and rhododendrons and keeping the bark moist seems to help buds sprout. And a year after pruning you will need to thin all the vigorous shoots and pinch out their tips (of the ones you leave) to develop a nice mound of growth – otherwise you end up with tower of vigorous growth.
The Biking Gardener 
This post is really giving me hope (not) for the little camellia I got last summer in lidl or aldi. I have alkaline clay soil and a very exposed site. I have found a little sheltered spot for it (away from morning sun I was told) and there are definitely a few buds but not sure if they are the fat ones you are referring to… will know for sure in a few weeks I guess!
Sorry my comments have not given you encouragement! You are right that avoiding an east-facing spot can reduce frost damage on opening flowers. Alkaline soil is not great but you can add sulphur chips to acidify the soil and/or water with acid plant food to help. Good luck!
We grew acres of camellias; but they left the farm before they needed more than minor trimming to enhance density. Stock plants were pruned only because cuttings were harvested from them. If we needed to prune camellias, it was because they had gone unsold for too long. However, I know that pruning them is no problem.
Camellias planted in the woodland gardens at Mount Congreve have made considerable size, as you can imagine, and there has been a programme of pruning over the last five or so years. Camellias of three/four metres have been reduced to 50cm and new growth has been vigorous.
Yes I have seen them, and the pieris, cut down really hard and their regrowth is amazing.
Are azaleas similar in this way? I love camellias, don’t have any yet. I would like to get a rhododendron for a shadier area of my back garden.
Azaleas and rhododendrons need the same basic conditions as camellias and are not happy in heavy clay or limey soils. Shade is not an issue though. An option is the Inkarho rhododendrons. These are standard varieties grafted onto a special, lime-tolerant rootstock. They are branded as Inkarho rhododendrons. They are recommended for pH up to 7. Although the original plant was discovered growing in a limestone quarry and then propagated as a rootstock they are not recommended for very limey soils. It is an option though, if you can get them.