Cloudy, rainy days coupled with the shade provided by nearby plants and structures can significantly reduce the amount of radiation available. Plants survive only where the amount is within a specified range. Plants survive only where temperatures allow them to metabolize. Plants differ in ability to survive frost, their responses varying from immediate death to sustained performance. The previous environmental and cultural conditions of plants can often shift, but not permanently alter, their tolerance to freezing.
Plants survive only when they are adapted to subfreezing weather.
The thermal cutoff temperature varies widely from species to species. By tradition we group plants into sun, partial sun, and shade types and plant them according to their light and heat tolerances. Gardeners need to know how much water a landscape plant requires in determining its usability in low maintenance landscapes. Rainfall gardening often greatly limits which species can be used successfully. Gardeners also need to know how much and how often to water plants in high maintenance landscapes.