Forestry Basics
Defects cause a reduction in the amount of lumber that can be obtained from a given log at the sawmill.  Typical mills are most concerned about defects on a tree stem, such as rot, splits, cracks, and curvy forms.
In addition to volume loss, the value of lumber that can be sawn from a given log depends on factors such as the presence or absence of knots (caused by branches). Trees can be graded according to a system that takes into account the amount of volume and the quality of the lumber that will be lost from the log when it is sawn. Logs given "Grades" where:
  • Grade 1 logs are the straightest logs with little or no defects.
  • Grade 2 logs have some defects.
  • Grade 3 logs have the most defects and can also have somewhat curvy stems.
Logs that are too curvy to be sawn, or have too many defects, are typically sold as pulpwood. The value of trees is related to their grade and species, with Grade 1 trees being worth more than Grade 3. The highest value category of sawlog is called "veneer". This grade of log is typically peeled at the mill and used in the manufacture of fine furniture. For most species (except for black cherry), veneer logs tend to be larger in diameter than Grade 1 sawlogs and have no defects.

If a landowner selling timber is not familiar with how tree grade is related to tree value, they may not receive a fair price for their timber. A landowner can gain a fair appreciation of the quality of their trees using observation and common sense. If trees are large with few knots showing on the lower (larger) logs, and stems are straight with no damage or rot then the logs will tend to be of high value. If there is evidence of a lot of stem rot in lower logs and many branches and crooked stems, then the trees probably have lower value. Tree species is also a very important factor determining tree value.        

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The following pictures illustrate some examples of defects in standing trees as well as a high value sawlog. 


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