Page "Dendrochronology" Paragraph 7

The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid ( hence the wood is less dense ) and is known as " early wood " or " spring wood " or " late-spring wood ".

The outer portion is the " late wood " ( and has sometimes been termed " summer wood ", often being produced in the summer, though sometimes in the autumn ) and is denser.

" Early wood " is used in preference to " spring wood ", as the latter term may not correspond to that time of year in climates where early wood is formed in the early summer ( e. g. Canada ) or in autumn, as in some Mediterranean species.