What is a tree?

You know a tree when you see one but putting it in words is not always so easy. The generally accepted definition of a tree is that it is a plant with a more or less permanent shoot system that is supported by a single woody trunk.

Trees are extremely successful organisms. With more than 80,000 species growing worldwide, 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 branch near the ground and have several narrow stems rather than the single trunk. The structural make up and properties of shrubs and trees differ. Having several stems means a shrub can support many leaves but these are less rigid than a single thick tree trunk is.

Trees are the tallest free-standing organisms in the world. They live longer and become more massive than any other living organism on earth.