What is going on with these warm 60-degree days in January and February? Is it spring already? Many daffodils are in full bloom on south-facing slopes in Chattanooga. Maple trees have big red buds. The grass never did get brown this winter. Unusual temperatures like this cause us to investigate what is normal.
Hardy plants
Plant scientists and climate experts put their knowledge together from temperature data collected from 1976 to 2005. They made a map of 13 hardiness zones for perennial plants of the United States. Each zone is the average of lowest winter temperatures for a given location for this time period. The map is based on the average annual minimum winter temperature, divided into 10-degree Fahrenheit zones.
Zone 1 would be places such as Alaska, while Zone 13 would be tropical, such as Hawaii. The greater Chattanooga area is in Zone 7, which has an average annual minimum temperature of between zero and 10 F. We can subdivide into Zone 7a (higher elevations around the city) and slightly warmer Zone 7b (the lower Tennessee Valley areas). Most garden centers will have charts or plant tags stating which perennials are hardy for each zone.
Plants are survivors