There are two main times that you can really shape any hedging that you may have in your garden. Clip at the end of May after any chance of frost has past and around now until the end of September. This gives the new cuts time to harden off before the first frosts come towards the end of October.
You can trim any hedge into a shape – the more dense the foliage, the better, and if the hedge is an evergreen, then you can enjoy the fruits of your labour into the winter months when there may be little else to provide any structure in your garden.
In my opinion, the best hedging plants for topiary are the most commonly used ones. Buxus Sempervirens, more commonly known as box, is the most regularly used hedging for topiary and can be highly clipped into all manner of shapes.
Timing when clipping box is very much of the essence and not just when in the year, but also when during the day. If you cut any plant in heat – particularly box – then the cut part of the plant is going to scorch and die. If it’s hot don’t start clipping until around six in the evening and give the plant a good soaking so it can cool before the sun rises again.
Yew or Taxus Bachata is also great for topiary and has been used to create amazing examples of the art for hundreds of years.
Ligustrum Japonicum is another fantastic topiary plant. It can be used to great effect when Japanese cloud pruning. It takes a good shape and is fast-growing, so will normally need three or four trims in the season.
There are some tried and tested rules when carrying out topiary tasks that can be used on all species.
Before you go outside, look to your tools. Anything that you intend to use to cut and trim the plant needs to be sharp. Using blunt tools will prevent you shaping anything properly. Also, making ragged cuts can lead to introducing infections into the plant.
Ahead of making your first cut, stand back and look at the plant, look at its form and what shape it might want to be made into and where to cut.
Use trimming oil and sterilise your tools regularly. I use a can of WD40 to oil the cutting blades and mechanisms of the tool and some Jeyes fluid mixed into a spray bottle to sterilise the blade so you are not passing any infections around the plant.
Take your time and do not take too much off too quickly. You can always take more off, but you can’t put more on!