Tucson sits at 2,410 feet in the Sonoran Desert, where sandy caliche soil defines nearly every landscaping decision across the valley. That caliche hardpan blocks root penetration and pools water during the summer monsoon rains that deliver most of the city's 12 annual inches in just a few months. Organic mulch plays a double role here, insulating roots from temperatures that routinely top 100 degrees while slowly building organic content in a lean desert substrate. Neighborhoods in Casas Adobes and Catalina Foothills sit on some of the densest caliche deposits in the region, making quality soil amendments essential for any new planting bed. Further south in Sahuarita, decomposed granite and river rock complement the native desert palette that The Old Pueblo has always embraced.