A gardening zone map shows the average temperatures in different areas so gardeners can decide which plants grow best in their location. To use these guides, choose an area on the map and match it to a corresponding color coded temperature chart.
The most commonly used chart is the US Department of Agriculture Plant Hardiness Zone Map, which shows the average low temperatures across the United States. Gardeners use this to determine which plants will survive the winter in their area.
The American Horticultural Society Heat Zone map averages the warmest days of the year for each region. Growers use this map to see if their climate will support tropical or non-tropical plants during the summer growing season.