Secondary growth in plants is the growth that results from cell division in the cambia or lateral meristems and causes the stems and roots to thicken/30%3A_Plant_Form_and_Physiology/30.04%3A_Stems_-Primary_and_Secondary_Growth_in_Stems). It occurs in most seed plants, but monocots usually lack secondary growth. If they do have secondary growth, it differs from the typical pattern of other seed plants. Secondary growth is characterized by an increase in thickness or girth of the plant, and it is caused by cell division in the lateral meristem/30%3A_Plant_Form_and_Physiology/30.04%3A_Stems-_Primary_and_Secondary_Growth_in_Stems). The process of secondary growth is controlled by the lateral meristems in both stems and roots, which include the vascular cambium and cork cambium. As long as the lateral meristems continue to produce new cells, the stem or root will continue to grow in diameter. In woody plants, this process produces wood and shapes the plant into a tree with a thickened trunk.

Primary growth, on the other hand, is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate, and gives rise to primary tissue/30%3A_Plant_Form_and_Physiology/30.04%3A_Stems_-Primary_and_Secondary_Growth_in_Stems). Most primary growth occurs at the apices, or tips, of stems and roots, and it is a result of rapidly-dividing cells in the apical meristems at the shoot tip and root tip/30%3A_Plant_Form_and_Physiology/30.04%3A_Stems-Primary_and_Secondary_Growth_in_Stems). Subsequent cell elongation also contributes to primary growth. The growth of shoots and roots during primary growth enables plants to continuously seek water (roots) or sunlight (shoots) /30%3A_Plant_Form_and_Physiology/30.04%3A_Stems-_Primary_and_Secondary_Growth_in_Stems).

In summary, primary growth extends the root/shoot axis and produces branch roots and shoots, while secondary growth increases the width of the plant root or stem, rather than its length.