One can judge comparative density, and therefore to some extent weight and strength, by visual inspection.
The conclusions of the U.S.Forest Service regarding the effect of rate of growth on the properties of Douglas fir are summarized as follows: "1.

In general, rapidly grown wood (less than eight rings per inch) is relatively weak.

A study of the individual tests upon which the average points are based shows, however, that when it is not associated with light weight and a small proportion of summer wood, rapid growth is not indicative of weak wood.
"2.

An average rate of growth, indicated by from 12 to 16 rings per inch, seems to produce the best material.
"3.

In rates of growths lower than 16 rings per inch, the average strength of the material decreases, apparently approaching a uniform condition above 24 rings per inch.