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Tree Biology

The easiest definition is that a tree is a plant with a more or less permanent shoot system that is supported by a single trunk of wood.

Trees are the tallest free-standing organisms in the world. They live longer and grow larger than any other living organism on earth. There are more than 80,000 species growing worldwide and they come in all shapes and sizes; from tiny Arctic Willows a few centimetres high, through to giant Redwoods over 100 metres tall.

Trees differ from shrubs. Shrubs normally grow near the ground and sometimes have several narrow stems rather than one single trunk. Shrubs can support many leaves because of their many stems. However, their overall structure is less rigid than one single, thick tree trunk.

Single Stemmed Trees Leighton  Shrubs Snowdonia
Single stemmed trees at RFS Leighton
Shrub showing multiple stems at
the RFS Whole Society Meeting, 2009