by Eric Meier
The Carya genus (or what is more commonly referred to as Hickory) is divided into two main groupings: true-hickory, and pecan-hickory. Species in the true-hickory group tend to be slightly denser, and therefore a bit harder and stronger than the species in the pecan-hickory group. However, because the two ranges of densities so closely overlap, using the weight of the wood to separate hickory is unreliable.
Distinguishing between these two groups of hickory is fairly straightforward. The quickest and easiest means of differentiating them is by observing the bands of parenchyma—in pecan-hickories, the bands are present in both the earlywood and latewood portions of the wood. In true-hickories, the bands of parenchyma are absent from the earlywood portion of the wood.
The sample of Shagbark Hickory on the left lacks parenchyma bands in the earlywood zone—characteristic of true-hickory. The sample of Pecan on the right shows uninterrupted bands even through the earlywood zone, indicating pecan-hickory. (Click for enlargements)
In addition to the continuous parenchyma bands (in reticulate pattern), another indicator of pecan-hickory is a tendency to be more semi-ring-poroous rather than strictly ring-porous, with a more gradual transition from the larger earylwood pores to the smaller latewood pores. However, although the two groups of hickory can be reliably separated, identifying particular species within each grouping is usually not possible.