Eristysvyöhykkeet

Eristysvyöhykkeet, known in English as "insulation zones" or "hardiness zones," are a system used to categorize regions based on their average minimum winter temperatures. These zones are crucial for gardeners and farmers to determine which perennial plants are likely to survive the winter in a particular area. The most widely recognized system is the USDA Plant Hardiness Zone Map, developed by the United States Department of Agriculture.

The system divides geographic areas into ten major zones, numbered 1 through 10, with each zone representing a 10-degree Fahrenheit (about 5.6-degree Celsius) difference in average annual minimum temperature. Zone 1 is the coldest, with average annual minimum temperatures below -50 degrees Fahrenheit (-46 degrees Celsius), while Zone 10 is the warmest, with average annual minimums between 30 and 40 degrees Fahrenheit (-1 and 4 degrees Celsius). Each zone is further subdivided into 'a' and 'b' subsections, representing 5-degree Fahrenheit increments.

The concept of eristysvyöhykkeet helps horticulturalists select plants that can withstand the lowest expected winter temperatures in their specific location. A plant labeled as being suitable for Zone 5, for instance, is expected to survive typical winter minimums in Zone 5. However, it's important to note that these zones are based on average minimum temperatures and do not account for other factors affecting plant survival, such as frost dates, humidity, rainfall, or soil conditions. Therefore, while a valuable tool, eristysvyöhykkeet should be considered alongside other local environmental factors when making planting decisions.