Thing are not that simple when we consider tree species. If we wander through a forest in Central Kentucky, we will see dozens of species of oak. There are Shumard, pin, scarlet, red and black oaks, among the red oak group. The problem may not be our ability to recognize species. We refer to these individuals as interspecific hybrids .
Interspecific hybrids are common in many tree genera.
Some genera, such as Fraxinus , do not appear to hybridize readily. The extent of hybridization in many genera is not well known, especially among tropical trees. At higher levels of classification, hybridization is rare, so that we rarely see intergeneric hybrids in nature. A precise definition of species is not nearly as important as an understanding of the species concept. Species do hybridize in nature, and the boundaries between some species are blurred.