Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots. Although "tree" is a common word, there is no universally recognised precise definition of what a tree is, either botanically or in common language. [1][2] In its broadest sense, a ... Trees can live for many years. The oldest living tree found is about 5,000 years old. The oldest tree from the UK is about 1,000 years old. [verification needed] The four main parts of a tree are the roots, the trunk, the branches, and the leaves. Wired: 900 Years of Tree Diagrams, the Most Important Data Viz Tool in History...