Shears in hand by the gate one August, I was trimming four boxwood balls that had come out of gallon pots in spring. I took a little off each one every few weeks, never much, and the surfaces thickened from the inside. Starting a topiary depends on the shape you picked. Balls, pyramids and cubes get cut against a template from year one, while a standard means one staked stem and several years of waiting.
The first cuts you make when starting a topiary matter more than any that come later. UGA Extension has measured where the response shows up. The strongest new growth always breaks within 6 to 8 inches (15 to 20 cm) of the cut. Every light trim pushes fresh shoots right where you want the surface to fill in, so clip small amounts and clip often. Skip two seasons and the plant spends that energy on long bare stems instead, and cutting harder later will not buy back the density you missed.
People starting a topiary often reach for advice written about hedges, and it does not transfer. Heading new plants back to within 12 inches (30 cm) of ground level builds the compact base a hedge wants. That is hedge guidance. Cut a plant you mean to shape on its own that low and you throw away the framework the whole thing depends on.
Simple geometry is where you should begin. You can cut them by eye once your eye is trained, though a template or a simple wooden frame held against the plant keeps the sides honest. I cut the outline of a half circle from scrap plywood. I checked each ball against it as I clipped, and my first pair came out even enough that nobody asked.
A standard follows a different method from day one. Training a topiary standard begins with choosing one strong upright shoot as the main stem and tying it to a stake. Every other shoot comes off. After that you clear the lower stem a few side branches at a time as the plant gains height, rather than stripping it bare in one go. Reaching the height you want takes several years, and nothing speeds it up.
Birds, spirals and other detailed shapes need a frame of galvanized or plastic-coated wire, and it belongs over the plant early while the growth is still short. The stems fill the frame from inside and you clip whatever pokes through the wire. Drop a frame over a bush that has already grown large and you spend the next two years fighting branches that went the wrong way.
Two limits keep a young topiary plant moving in the right direction. Never take more than one third of the crown in a single year, however far the shape has drifted from what you wanted. And spread a mulch of organic matter each spring, because all that clipped growth has to be replaced by something.
Choose a ball, pyramid or cube for a first try, or commit to a standard and accept the longer wait.
For a standard, tie one upright shoot to a stake and cut every competing shoot off at the base.
Cut the outline from scrap plywood for a simple shape, or set a wire frame over the plant while growth is still short.
Take small amounts through the growing season so new shoots break close to each cut and the surface thickens.
Remove the lowest side shoots of a standard a few at a time as height builds, never the whole stem at once.
Mulch with organic matter each spring and keep any single year of cutting under one third of the crown.
Read the full article: Topiary: How to Shape Plants Without Killing Them
