Trees and shrubs
- A tree is a woody plant with a single, well-developed stem – the trunk or bole -which branches well above ground level.
- A shrub is a woody plant with several stems that branch at or close to ground level. It is generally smaller than a tree.
These definitions are not clear-cut. Some shrubs can be taller than some trees; some trees produce additional trunks, and a few have no trunk at all! So the terms tree and shrub are really just convenient labels.
The two diagrams below show the basic structure of a tree.
Plants need light in order to grow, so tall trees often have an advantage as they can reach the light without much competition from other plants.
A trees increases in height and girth each year. As it expands in girth, it leaves a ring of cells marking that year's growth. You can tell the age of a tree that has been cut down by counting the number of rings in the trunk.