Blackland Prairie

The Blackland Prairie is a 200-mile band of dark, deep clay that runs from the Red River south through the DFW metroplex, Waco, Austin, and San Antonio. It is one of the most productive agricultural soils in Texas but also one of the trickiest for gardeners because the heavy clay shrinks and swells with moisture. Plants that thrive here tolerate clay, drainage swings, and the urban heat of the I-35 corridor.

Conditions: Heavy black clay, alkaline-to-neutral pH, 30–40 inches annual rainfall, hot humid summers with occasional hard freezes.

Cities and areas: Dallas, Fort Worth, Plano, Frisco, McKinney, Austin, San Antonio, Round Rock, Waco.