Virtual Museum of Canada
Jardin botanique de Montréal 
Centre for Forest Research

Small, but solidly built

Roots add girth, just like the trunk and branches. Growing in diameter is called secondary growth. For humans, you could say that our primary growth, in length, is when we grow taller, whereas our secondary growth, when we add girth, starts when we put on a belly!

Without this secondary growth, the roots wouldn't be able to anchor the tree. As they add girth, the roots growing next to each other can form a tight web, or a root growing near a rock can wind itself firmly around it.

Secondary growth is possible because of cambium (Cells responsible for the increase in thickness of the trunk, stems and roots of many plants.), which contains undifferentiated cells, like the ones found in the meristems (Tissue composed of cells able to divide into new specialized tissues.) of buds, or under the root caps.


Schematic of a root cutting showing all its tissues
Secondary growth
© National Research Council Of Canada, NRC Research Press
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