A Chrysanthemum plant, when left to grow naturally, will continue to grow taller until a terminal bud is formed at the tip of the main stem. Side-shoots will then form in the leaf axils. Pinching out, or stopping, is purely a way of hastening the formation of these side-shoots. Simply remove the tip of the plant, leaving 4 - 5 leaves. If, at the time of pinching out, there is any sign of a terminal bud, it is essential to remove a large piece of the plant, sometimes over half.