summerwood

Summerwood, in wood anatomy, refers to the portion of an annual growth ring formed later in the growing season, typically during the warmer, drier part of summer. It contrasts with springwood (earlywood), which forms at the beginning of the season when growth is rapid and conditions favor larger cells.

In softwoods, summerwood consists of tracheids with smaller lumens and thicker walls, producing higher density than earlywood. In hardwoods, the cells in the late portion of the ring are also smaller with relatively thick walls, yielding a darker, tougher zone. The transition between earlywood and summerwood contributes to the characteristic banded appearance of many growth rings.

The presence of summerwood helps define the ring boundary and influences the timber’s density, hardness, and dimensional stability. It is a key feature in dendrochronology for dating wood and in wood science for assessing mechanical properties. The degree of contrast between springwood and summerwood varies among species and climates; in some species the distinction is pronounced, while in others it is subtle or less evident. Summerwood terminology is often used interchangeably with latewood in some texts, though latewood more typically refers to the entire zone of denser cells formed later in the growing season.