A growth ring, also called an annual ring, is the ring a tree adds to its trunk each year, visible in sawn timber as a series of concentric rings. In temperate climates each ring represents one growing season; by counting the rings you can determine the age of the tree.
Structure of a growth ring
A growth ring consists of two parts:
- Earlywood (spring wood) — light, porous wood formed quickly in spring
- Latewood (summer wood) — dark, denser and stronger wood formed later in the season
The contrast between light and dark makes the rings visible. Wide rings indicate a favourable growing year; narrow rings point to drought or unfavourable conditions.
Significance for construction
Growth rings say a lot about the quality of building timber:
- Strength — timber with many closely spaced rings (slow growth) is often stronger
- Movement of wood — the orientation of the rings determines how wood shrinks and warps
- Sawing — quarter-sawn or plain-sawn timber results from the cut direction relative to the rings
- Dendrochronology — dating timber and buildings from the ring pattern
Related Terms
- Annual ring
- Timber
- Movement of wood
- Dendrochronology
- Quarter-sawn
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