Crepe Myrtle Tonto Hardiness: Reliably top hardy to U.S.D.A. Zone 7b, root hardy to U.S.D.A. Zone 6 . In addition to field resistance to powdery mildew, the hybrids provide new trunk colors that in the future may be sought as much as the brilliant flowers. Description: Culture: Plants grow best in full sun in reasonably heavy loam to clay soil with a pH of 5.0-6.5. Adaptable to a wide range of landscape conditions. Landscape Use: Specimen plant, trained single stem as a small tree, informal tall hedges, background for perennial border, or in containers. Adaptable for home garden, parks, industrial complexes, roadsides and malls.