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. The most common Hickory sub-species sold in the US is Shagbark Hickory, also called True Hickory.