Apical dominance is a phenomenon in which the growth of the top shoot impedes the growth of other lower shoots. This inhibition of the growth of the lower shoots is caused by a plant hormone called auxin.
The top shoot or bud, which is called the apical meristem, contains the greatest amount of auxin. A meristem is a special type of tissue that produces new cells. When this top bud or meristem is snipped off, lower shoots, called axillary buds, can grow. In this way, gardeners can create bushier plants by allowing the lateral stems to develop. When the apical meristem is intact, the axillary buds display no active growth and are dormant. This dormancy is caused by the presence of auxin.