The function of the cambium is to produce layers of phloem and xylem in a woody plant, thereby increasing the diameter of the stem. It is a thin layer of tissue that lies between the bark and the wood of a stem, and it is most active in woody plants.
The cambium promotes secondary growth of stems and roots, which is the growth that occurs after the first season. In addition to increasing the tissue layer of the stem, the cambium may also function in healing for injured plants. When this happens, the cambium forms within callus tissues, which are the cells that grow over the surface of the injured plant.