Plant hardiness zones are used to predict plant survival based on what factor?

• A. Average rainfall
• B. Summer maximum temperatures
• C. Soil type classification
• D. Winter minimum temperatures

Answer: (D)

Plant hardiness zones predict whether a plant will survive winter based on the coldest temperatures it can withstand. The zones are defined by the average minimum winter temperatures in a region, because winter cold is the main limiting factor for perennial plants. If winter lows fall within a plant’s tolerance, it’s likely to survive and regrow in spring; if not, it may be damaged or killed. While rainfall, soil type, and summer heat influence other aspects of growing success, they do not determine winter survival as directly as the minimum winter temperature does. So, the winter minimum temperatures are the primary factor used to forecast plant survival.