Moisture is the overriding factor governing fuel flammability. It determines whether ignition will take place and to what depth the forest floor will be consumed. If one uses enough torch mix, he/she can ignite the immediate area, but if fuel moisture is much above 22% in pine litter or 16% in hardwood litter, a headfire is mandatory and even then the burn will be patchy at best when the terrain is relatively flat. Although I am not aware of any supporting field data, laboratory fires on steep slopes (typical of the Piedmont and southern Appalachians) will spread with dead fuel moisture approaching 35%.