Rod Haenni has explored the hardiness of thousands of different cacti and other succulents in different settings and microclimates. All of the plants were subjected to below zero Fahrenheit every winter, including polar vortexes that may arrive in the fall and spring, dropping the temperatures from 60-70F to near or below zero in less than 48 hours.

Rod has created two lists of cold hardy cacti and succulents:

• Current List of Cold Tolerant Cacti/Succulents in my Gardens
• A Frequently Consulted Cold Tolerant Cactus and Succulent Annotated Bibliography