The origin of the word scrub reaches back into Middle English as a variant of shrub, which was often considered a kind of failed tree. In nineteenth-century American usage, the word always implies this sense of the inferior, a kind of mongrel or deficient quality. Not just scrub-oaks and scrub-pines, but scrub horses (the exact opposites of purebreds), and scrub baseball players (far below the first string). Scrublands, then, are tracts considered to have little commercial value, overgrown with low, stunted trees, brushwood, underbrush. In the wetter climates of the East, scrub is often a temporary, intermediate stage in the process of plant succession, as denuded land heals itself back to forest. In drier climates, where there is a deficit of water, it is a more permanent plant community, for example the sage scrub of the West, or the upland sand-pine and palmetto scrub of Florida.

Charles Frazier