There are over 281 species of woody plants and 32 species of cacti in the South Texas ecological region. The vast majority of these are found in the lower Rio Grande Valley, which is part of the subtropical Tamaulipan biotic province. Many of the plant species in this area reach their northernmost boundary here. The 44 plants described in this guide represent an estimated 75% of the overall brush biomass of the South Texas ecological region, excluding the lower Rio Grande Valley.
The plants are grouped into thorned and thornless categories and alphabetized by family. Distinguishing characteristics have been italicized for easy reference. Similar species are also noted. In this guide, plants are not ranked by importance because their value to animals can differ from ranch to ranch, depending on the plant's availability and the ranch's location, soil type, and land management practices. In case a plant is not found in this guide or more information is desired, a list of additional references is included.