There is a tree that grows commonly in the mountains of the Southwestern United States, which science currently calls Quercus rugosa, a tree we will be referring to as the Southwestern Netleaf oak. This tree is distinctly different from the tree also called Quercus rugosa, but found in Mexico and areas south, which we will be referring to as the Mesoamerican Netleaf oak.

The Southwestern Netleaf oak is consistently smaller in stature than its mesoamerican cousin, ranging in height from 5 feet, to about 40 feet at a maximum. Mesoamerican Netleaf oak can reach 100 feet in height. The Southwestern Netleaf oak also has smaller, to much smaller, leaves, which are actually quite variable in shape, suggesting strong introgression from neighboring oaks. Many of these leaves look radically different from the leaves of the Mesoamerican Netleaf oak.

The Southwestern Netleaf oak used to be known as Quercus reticulata, due to its clear difference from the Mesoamerican Netleaf oak. Lumping these species together is a powerful impediment to those wanting to describe these two very different trees, while simultaneously introducing them to the nursery trade, which is our current situation in California.

At least one of our large commercial nurseries purchased Southwestern Netleaf oak acorns when they wanted to grow the Mesoamerican Netleaf oak, a confusion which could undermine the introduction of both trees, with their very different places in planted landscapes.

This discussion is an example of the old battle between those who favor inclusion of a wide range of organismic forms within a single species (lumpers), and those who advocate for finer, pragmatic distinctions (splitters). The lumpers currently rule Netleaf oak taxonomy, forcing us to write these confusing paragraphs, in an attempt to keep very sad landscape mistakes from being made.