The growth of stems is most previlant in perennials because they have the same stem each year. The greatest increase in growth occurs at the tip as cells in the apical meristem, which make up the primary tissue, divide. These newly formed cells than begin to grow larger in an area behing the meristem called the zone of elongation. Continuing back from the Zone of Elongation is the Zone of Maturation. As well as the stem increasing in length, it also increases in thickness year after year. The increase of thickness is produced by the vascular cambium and the cork cambium, creating a new layer of thickness.
