"Second-growth hickory has better
strength than old-growth hickory because second-growth trees have had
less competition and grow more rapidly. Old-growth hickory that grew
more and more slowly in dense forests had a good deal of light, brash
wood. In such old trees the sapwood, or white-hickory portion, was the
weakest part of the whole tree. For a long time hickory buyers avoided
certain areas of old-growth forests in their search for stock of high
strength and toughness. More recently, as good hickory has become
more difficult to find, many buyers have learned to select hickory on a
basis of its growth rate, from either old growth or second growth, and
thus have obtained considerable amounts of strong hickory from the
more rapidly grown trees of both."
https://naldc.nal.usda.gov/naldc/download.xhtml?id=IND43893951&content=PDF
Bob