Palmpedia - Palm Grower's Guide:PALMPEDIA SURVIVABLILITY INDEX
Palmpedia has devised a new way to index the cold hardiness of palms. Categories are created based on the observation of a surviving species, instead of climate zones and temperatures. The simple presence of a mature palm sends an unmistakable message of what other species will survive in the same area. A mature Queen Palm in a neighborhood would indicate that any palm hardier than a Queen will also survive.
Based on this reasoning, Palmpedia will rank palms according to their relative hardiness. That way, spotting a mature palm will provide a grower with a reference, and a list of palms that will also survive in the same vicinity. It should also provide a sliding scale indicating which palms might also have a chance, and those with little hope.
The survivability of a palm is determined by more than just an ultimate low temperature. Both Mediterranean and Subtropical climates experience periodic freezes that may kill certain palms. However, the prevailing daytime temperature, duration of freezing temperatures, and the humidity play an important role in which palms will survive. Therefore, Palmpedia will devise two indices. One for Mediterranean climates, such as Southern California, that is characterized by cooler overall winter temperatures, and lower humidity. And another for Subtropical climates, such as central Florida, characterized by mild winter temperatures, and higher humidity, yet still experience occasional freezing temperatures.