Many parts of the Rio Grande Valley of Texas have excellent soils rich in river sediments. Additionally, the climate is apt for growing a variety of plants. However, many gardeners find it challenging to garden in this region of Texas. For example, many roses are not suitable for certain parts of the Rio Grande Valley, and may struggle to grow here. However, by properly adjusting the soils, they can indeed grow. Look for tropical and subtropical varieties of plants to grow in this region.
For more information, see this Aggie Horticulture website about plants appropriate for the Rio Grande Valley of Texas.