Secondary growth

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.

Secondary growth is a term in botany. It usually occurs in dicots and gymnosperms. It makes the stems and roots thicker. It is one of the features of trees whereby they come to have long lives.

Tree growing around a lamp post, an example of secondary growth.

Monocots and Pteridophytes usually lack secondary thickening, with the exception of Isoetes. That is a quillwort, a genus of lycopods.