The Angiosperm Plant Body

How many years' growth does the length of twig below represent? To find out, you must understand how bud scale scars represent annual growth. When the terminal bud breaks dormancy in the spring, the bud scales eventually drop away, leaving bud scale scars that form a circle around the stem. These scars remain at this place on the stem. But the newly emerged shoot grows for the whole growing season, laying down a new length of twig. Finally the twig growth slows and stops, and a new set of bud scales protects the twig's terminal bud for the winter. The distance between one year's bud scale scars (a close set of rings encircling the twig) and another year's bud scale scars is one year's growth of that twig. Note that twig scars (like branch scars on old tree trunks) can be obscured by secondary growth, but usually only after three years.

It would take a tree three years to manufacture a length of twig like the one shown above.