Secondary growth is the increase in thickness of root or stem due to the activity of lateral meristems (vascular cambium and cork cambium). With few exceptions most of the dicots and gymnosperms show secondary growth. Roots and stems of monocot plants do not show secondary growth (due to absence of vascular cambium), with few exceptions e.g., Dracaena, Yucca, etc., which exhibit anomalous secondary growth.