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Reporting
Dahlias are hardy to zone 8Dahlias are hardy to zone 8 where they can be cut back and left in the ground to overwinter. In zone 7b, dahlias sometimes overwinter in the ground depending on the severity of the winter. It is recommended the tuberous roots be lifted and stored during the winter. Northern Utah has several different zones. See the USDA Hardiness Map for your zone: http://planthardiness.ars.usda.gov/PHZMWeb/