Topiary plants were once found only in formal gardens or on the estate grounds of the wealthy. Today, gardeners everywhere enjoy creating these living works of art by trimming and shaping plants into specific forms. Topiaries range from simple geometric shapes to complicated designs made from several combined plants. A spiral is a basic topiary shape simple to create at home.
Select an upright tree with a straight trunk. Yews or Alberta spruces are recommended choices for spirals because they have short lateral branches and fine needles that respond well to trimming. Choose a small tree so you can reach the top easily.
Tie one end of the string at the top of the tree. Wind the string around the tree from the top to the bottom to mark the spiral shape. Leave a foot or more between the spirals of the string to allow plenty of room to create the spiral shape.
Use the pruning clippers and carefully trim back the branches along the path of the string. Some branches may need to be removed all the way to the trunk, while others will need only some shearing. This pruning outlines the basic form of the spiral in the tree's lateral branches, and creates the structure the spiral will follow as the tree grows.
Remove the string when the basic form has been pruned into the tree. Use the small trimming clippers to smooth out the shape of the spiral, rounding off the edges as necessary.
Maintain the spiral shape as the tree grows. Shear stray growth to keep the spiral shape. Trimming encourages new, small branching growth, which will fill in and cover blank areas.
To control the height of the spiral topiary, let the tree grow as tall as you desire, and then cut off the top of the tree. Trim the tree so it blends with the shape of the spiral and is not simply a flat top.