This method can be used on a number of deciduous or evergreen trees and shrubs. However, evergreens produce a more striking specimen and give all-year-round interest. Plants seen as cloud-pruned specimens include:

• Box (Buxus sempervirens)
• Yew (Taxus baccata)
• Pine (Pinus)
• Japanese privet (Ligustrum japonicum)

Other interesting specimens would be Phillyrea latifolia, Luma apiculata, Japanese holly (Ilex crenata), Camellia japonica and Osmanthus × burkwookii.

• Choose plants with interesting branch formations – these will make the basis of a design
• Hedges can also be pruned into large cloud shapes – this makes a nice change from straight edges
• Trees and shrubs can be bought already trained from specialist nurseries – these save time and effort, but can be expensive

Trim annually with secateurs or shears in early or late summer to keep specimens in shape. Faster growing species may need to be trimmed twice a year. Suckers and unwanted branches can also be removed. If you have chosen a flowering shrub, be aware that you will need to prune it after flowering, otherwise you will cut off the flowers.

You can start off with any size plant. However, there are a couple of things to consider;

• Cost: small plants will generally cost less and allow for more artistic licensing. Larger plants will be more expensive yet save many years of waiting for the plant to get to the desired height 
• Rate of growth: slow-growing species will take longer to reach a mature size so it might be worth buying a larger specimen or choosing another variety if time is a problem

Buying a ready-shaped specimen is always an option but if you want to have a go at shaping your own, here's how;

1. Select a plant with an interesting branch formation. It does not have to be symmetrical and equally sized – some of the most striking examples of cloud pruning are very unbalanced.
2. Work out which branches you would like to keep and how you would like it to look at the end. This is because, once the branches have been removed, it can take a very long time for them to grow back!
3. Using secateurs or a pruning saw, remove unwanted branches and twigs from the centre of the plant so that the main branches are bare. Ideally the cuts should be made when the plant is young as the pruning cuts will disappear with age leaving behind attractive bark.
4. If you wish for your plant to continue to grow taller and wider, do not prune the growing tips on the ends of the branches. These need to be kept intact until you have the desired length and height. The side shoots around the ends of the branch can now be shaped into a cloud shape.
5. Once you have the desired length and height, trim the tips and this will encourage branching and the cloud shape will begin to fill out.
6. The branches can be manipulated by using stakes or weights to get the shape you require.

This can also be attempted on existing trees and shrubs in the garden.

How to maintain existing specimens

It is important that you trim specimens annually with secateurs or shears in early or late summer to keep specimens in shape. It can take a while to recover shapes that have been lost. Plants with larger leaves look better if they have been pruned with secateurs as shears can leave untidy cut/damaged leaves, which are more apparent on larger leaves.

Some of the more readily-available specimens of cloud pruning are Japanese privet (Ligustrum japonicum). This is because it is quick growing and so reduces the overall cost. However, its speed of growth does mean it needs to be trimmed several times a year.

Plants that are cloud pruned can look very much like bonsai trees. The only difference between niwaki and bonsai is that bonsai are grown in containers and niwaki are grown in the ground. The size of the plant has nothing to do with the naming, it is purely from how it is grown. Both subjects are highly prized art forms with Japanese gardeners taking years to be qualified in this specialised area.

For a more in-depth look into this subject, refer to the book Niwaki: pruning, training and shaping trees the Japanese way by Jake Hobson (2008, Timber Press, ISBN: 9780881928358). It contains a full study of the subject and illustrates many beautiful examples. This book is also made available through the RHS Lindley Library.