How to prune topiary

Whether they are grown in a pair of sleek galvanised steel containers outside your front door or planted among perennials in a border, box topiary shapes are among the most useful plants in the garden, providing structure, texture and all year round colour.

Although box balls, cones, cubes, pyramids, domes, spirals and a menagerie of animal shapes are among the trendiest things you can grow, they quickly lose their appeal when a crisp outline is lost beneath a shaggy coat of new growth. The answer: give plants a trim in June.

When to prune topiary

Prune topiary in June. You might notice your box bursting into life in March and lots of lime-coloured shoots concealing the dark green shape beneath but d on't be tempted to prune them until June.

Trimming young, sappy growth in the spring is likely to bruise the foliage, leaving you with a topiary shape that is unsightly. It is best to prune in mid-June, when the leaves are hard and leathery, and again in late summer if necessary.

Don't worry if you did prune your topary in the spring, the bruising will be eventually hidden by the subsequent flush of growth.

How to prune topiary

It's possible to trim simple shapes – such as cones and balls – by eye, but for greater accuracy use a garden cane as a cutting guide for straight edges or make a template.   

To prune balls, take a length of garden wire and twist it into a circular shape that can be held and moved over the plant as you prune. To ensure you are left with a perfect sphere, make the frame smaller than the mass of foliage.

Restore a cone shape by standing above the plant and pruning in an outward direction from the centre, working around the plant. Alternatively, rest three canes on the sides of the cone and push into the ground. Secure the canes at the top to make a wigwam and bind the sides together with garden wire. Use your shears to prune to this framework.

Topiary spirals may look complicated, but it is easy to re-establish an overgrown specimen.  Working from top to bottom, prune the upper surface of the spiral making sure you remove the foliage as far back as the main stem. Next, trim the upper and then the lower turn of the spiral to create its curved edges.

Pruning tips

With practice, pruning topiary is a doddle. For the greatest success use a pair of hand held trimmers - these look a bit like sheep shears - to leave a lovely clean finish, and regularly step back to double check your progress – unfortunately, if you make a mistake there's no turning back.