Application. Clones of Eucalyptus grandis and E. grandis hybrids were naturally subjected to temperatures down to -6°C for 18 h in Florida. Locally adapted trees may be intensively screened to develop frost resilient candidates. Ortets must be further tested for vigor and frost resilience. Major commitments are needed to obtain satisfactory numbers of clones for operational use.Abstract. Eucalyptus grandis, E. grandis hybrid, and E. saligna hybrid trees, developed through as many as four generations of selection in southern Florida, were naturally exposed to exceptionally low winter temperatures. In a genetic base population and related field studies, 100 phenotypically superior cloning candidates were selected after an 8-h freeze with a low of -11 °C. Following propagation as rooted cuttings, 55 clones (typically 11-42 ramets per clone) were outplanted in a single-tree plot design and evaluated for 3.8 years which included two additional severe freezes. Significant clonal variation was observed in frost resilience, vigor, and quality. After composite evaluation for frost resilience, size, and form, only three clones were considered suitable for operational planting. Selection of further clones for outplanting requires major commitments to locate candidates and to test them. Field testing for frost resilience requires considerable investment, much beyond the requirements for developing fast-growing clones alone. Clones identified by testing will not be resistant to freezing conditions but will be resilient and greatly reduce the risks now associated with plantation culture in southern Florida.