Topiary is the art of shaping shrubs, a practice dating back to ancient times, when Romans, Egyptians and Persians clipped hedges into perfect squares. Modern topiary can be as fanciful as wild animals or as simple as geometric shapes including cones and boxes. One of the more difficult shapes to clip a topiary is a perfect circle. Rather than free-handing a topiary shape, use a guide when trying to achieve a perfect circle. Select a hedge with a branching habit. Shrubs such as boxwood or juniper grow back thicker after each trimming. The shrub you select should already be shaped roughly in a circle to make it easier to shape.
Measure the distance across the center of the shrub with a measuring tape. Cut a length of 9-gauge wire that is twice as long as this distance with a pair of wire cutters.
Melt a bead of soldier onto the tip of one end of the 9-gauge wire.
Flex the wire into a circle and touch the tip of the other wire end into the soldier bead. Hold the wire in place until the soldier solidifies. This wire will be your guide when clipping your hedge.
Soak a cleaning cloth in bleach. Swipe the cloth along the blades of your shears in between each cut made with your shears to prevent the spread of disease.
Hold your guide up with one hand, and with the other, prune away any branches that fall outside of your guide.
Trim away only 3 inches from the end of each branch. Schedule regular pruning sessions every three months to shape your topiary form. Work gradually toward the topiary circle, rather than trying to achieve it in one pruning session.