Secondary growth is the growth in thickness due to the formation of secondary tissues by lateral meristems. With the exception of some annuals, most of the dicots and gymnosperms show secondary growth in their stems and roots. It takes place by the production of two types of secondary tissues : secondary vascular tissues and periderm. These tissues are formed by meristems, vascular cambium and cork cambium respectively. Secondary growth does not occur in monocots because monocots do not possess vascular cambium in between the vascular bundles.