Secondary tissues are produced in woody plants. Secondary xylem and secondary phloem are produced from a cylinder of meristematic tissue within the woody stems and roots. This cylinder of meristematic tissue is the vascular cambium. The secondary xylem provides additional structural support and additional water conduction tissue in shrubs and trees. The secondary phloem replaces the primary phloem.
Similarly, as the trunk of a woody plant gets larger, the dermal tissue need to be expanded and replaced. New dermal tissue is produced by the cork cambium, which lies beneath the bark.