USA Flower Planting Zones

About the Zones

• The USDA has zones from 1 to 13; each zone has an "a" zone and a "b" zone, making for 26 zones altogether. The zones are based on the average annual extreme minimum temperatures, with USDA zone 1a being the coldest and USDA zone 13b being the warmest. The contiguous states only go up to zone 11; the warmer zones are found in Hawaii and Puerto Rico.

How to Use Them

• The area you live in is covered by one zone. Most states have two to three zones within their boundaries. The tree, shrub or perennial you choose must fall within your zone. For example, if you live in Fort Wayne, Indiana, you will need a plant that is hardy in USDA zone 6a. If you live in the northern part of Minnesota, you'll need plants hardy in zones 2 and 3. Some plant tags may say "hardy to zone ... ," meaning they are too sensitive to be planted in any zone below the listed one.

What About Annuals?

• Annuals are flowers that are planted for one season and that's it. They don't come back year after year. Many annuals planted throughout the United States are semi-tropical to tropical plants that are found in warmer regions. They can survive the warm summers of most USDA zones, but the first shot of frost can quickly do them in. Many of the annuals are hardy in USDA zones 10 and up, meaning they could potentially be perennials in these zones.

Other Growing Zones

• While the USDA planting zones are the standard, you may also find tags that list Sunset climate zones or heat zones. Sunset climate zones are based on year-round information, not just minimum extreme temperatures. Factored into these zones are elevation, latitude, ocean influence, mountains and valleys, and microclimates. Sunset has many more zones than the 13 basic zones of the USDA map. The American Horticultural Society offers another map: the Heat Zone map. This map of zones is opposite to USDA hardiness zones; it uses maximum extreme temperature averages to tell you if your climate gets too hot for a certain plant.