MICHIGAN FORESTS FOREVER TEACHERS GUIDE

MEASURING TREE AGE & RATE OF GROWTH

HOW TO USE AN INCREMENT BORER

  1.  Assemble borer, remove extractor. 
  2.  Push hard, the threaded end into a bark crevice, at dbh (4.5 feet from ground).
  3.  Turn clockwise.  Continue to push hard until threads are into the wood.
  4.  Use both hands to screw borer to the center of the tree.
  5.  Insert extractor slowly (avoid breaking and skewering your hand) and upside down.
  6.  Turn borer 1.5  times.
  7.  Gently pull out the extractor.
  8.  Count rings (estimate rings if tree pith is missed).
  9.  Add number if years for tree to reach 4.5 feet.   [5 years for aspen & softwoods, 10 years for hardwoods]
10.  Remove borer and blow it clean.
11.  Re-assemble borer.

Borer use in a sugar maple tree.       The increment core to the left shows 169 annual rings.  The center of the tree was missed, not showing approximately 4-5 rings.  The core was taken at 4.5 feet from the ground, so an additional 5 years should be added.  Total age is about 179 years.       Increment borers are expensive tools, in the range of $140 for a ten-inch, three-thread borer.  Borers can be purchased through Forestry Suppliers.  Type "increment borer" into the product search window.      Caution: Improper borer use can lead to breakage possibly causing injury to user, especially the hand.

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