Definition: The relative tolerance of the plant to calcareous soil. Calcareous soil is defined as soil containing sufficient free CaCO3 and other carbonates to effervesce visibly or audibly when treated with cold 0.1M HCl. These soils usually contain from 10 to almost 1000g/kg CaCO3 equivalent.
Definition: The ability of an organism to resist burning.
Comment: If a plant can carry a fire—and most can—it is scored as "not fire resistant" in the USDA PLANTS database where this characteristic is evaluated with reference to problem fires in California. http://plants.usda.gov/charinfo.html
Definition: The minimum tolerable temperature is the lowest temperature recorded in the plant’s historical range. If this is not available, the record low January temperature recorded at climate stations within the current geographical range of the plant is used. This definition does not apply to summer annuals.