First, box is a classic choice for topiary, it’s versatile and doesn’t grow too fast or slow, making it a great choice for trimming into shapes such as spirals, spheres, cones and even lollipop shapes.
Trim in late spring to encourage new growth of side shoots. Then, these new shoots can be trimmed in summer to establish the desired shape. Further trimming will encourage more growth, so in autumn the box can be tidied again if necessary. But don’t leave it too late in the season to do this as early frosts may damage the young growth.