Have you ever tried to trim a topiary? If you are following existing lines, it ususally isn't too trickly but if you are aiming to turn a cone into a spiral, it can quickly go off the rails. Topiary trimming is tricky and an overly zealous Edward Scissorhands inspired gardener can easily trim too much - causing a plant to take years to recover. But I have a trick for you - the ‘tape trick’ will help you get a perfect spiral every time.
Select a shrub or plant that is tall and full and has a long straight central stem. Evergreens such as boxwood or privet work well as do various junipers, yew, hollies and arborvitea. Trim the shrub to make a clean and neat cone.
Once you have a cone, start at the base and wrap masking tape around the plant all the way up to the tip to create a spiral that you are happy with. Don’t do too many twists. If you are trimming a set of plants, use the tape to help you match the spirals before you cut.
Following the line of the tape, trim back the foliage a few inches above and a few inches below the line. Taper the trim so that the longest branches remain under the tape.
Step back frequently to take a look at your progress and make adjustments.
Be patient—this will take time. When you are done, the plant will need to recover. More trimmings and giving the plant time to grow into the gaps will eventually give you a perfect twist.