Wood as a Building Material - Carpenter's and Builder's Math, Plans, and Specifications - page 54

Virgin and Second Growth
Occasionally an order calls for lumber of either virgin growth or
second growth. The terms, however, are without significance, as an
individual cannot tell one type from the other when it is delivered.
The virgin growth (which is also called old growth or first growth )
refers to timber that grows in the forest along with many other trees,
and, therefore, has suffered the consequence of the fight for sunlight
and moisture.
The second growth is considered as that timber that grows up
with less of the competition for sunlight and moisture that charac-
terizes first-growth timber.
Because of environment, the virgin growth is usually thought
of as wood of slow-growing type, whereas the second growth is
considered as of relatively rapid growth, evidenced by wider annual
rings. In such hardwoods as ash, hickory, elm, and oak, the wider
annual rings are supposed to indicate stronger and tougher wood,
whereas in the conifers such as pine and fir, this condition is supposed
to result in a weaker and brasher wood. For this reason, where the
strength and toughness are desired, the second growth is preferred
among hardwoods, and virgin growth is desired in conifers. This is
because of the following:
The variety of conditions under which both virgin and second
growth timbers grow
Virgin growth may have the characteristics of second growth
Second growth may have the characteristics of virgin timber
It is advisable in judging the strength of wood to rely upon its density
and rate of growth, rather than upon its being either virgin or second
growth.
Time of Cutting Timber
The time when timber is cut has very little to do with its durability or
other desirable properties if, after it is cut, it is cared for properly.
Timber cut in the late spring, however, or early summer is more
likely to be attacked by insects and fungi. In addition, seasoning
will proceed much more rapidly during the summer months and,
therefore, will result in checking, unless the lumber is shaded from
the intense sunlight. There is practically no difference in the moisture
content in green lumber cut during the summer or winter.
Air-Dried and Kiln-Dried Wood
There is a prevailing misapprehension that air-dried lumber is
stronger or better than kiln-dried lumber. Exhaustive tests have
conclusively shown that good kiln-drying and good air-drying have