Lateral growth of a plant axis (shoot axis or root) that is an increase in thickness resulting from formation of secondary vascular tissues by the vascular cambium.
Comment:
Occurs in vascular plants, including gymnosperms and most dicotyledons. Commonly supplemented by activity of the cork cambium or phellogen (PO:0005599). Monocotyledons do not have secondary growth, but may undergo primary thickening (GO:0080192) or secondary thickening (GO:0080191), which can give the appearance of secondary growth. Primary and secondary growth can occur simultaneously in the same organism.