When selecting vegetation for a sustainable garden, work with nature and choose plants adapted to the conditions of the site. These plants will minimize the need for fertilizers, pesticides, and irrigation and reduce the chance of failure and replacement costs. Consider the plant’s water and soil requirements as well as the hardiness zone and need for sun or shade.
Most plants available for sale at nurseries or through online suppliers have been assigned a hardiness zone based on a hardiness zone map. This is one of the most basic tools gardeners have used for decades to determine if a particular plant can survive winter in their area. Probably the best-known hardiness zone map in the eastern two-thirds of the country was produced by the U.S. Department of Agriculture (USDA). The most recent USDA map (www.usna.usda.gov/Hardzone/ushzmap.html ), published in 1990, divides the country into 11 color-coded bands or zones. Each successive zone represents a 10 degree Fahrenheit difference in average annual minimum temperature—the higher the number, the warmer the temperatures for gardening in that zone.
In 2006, using the same basic zone structure as the USDA, the National Arbor Day Foundation produced an updated map (www.arborday.org/media/zones.cfm ) for the U.S. based on more recent weather data.
Gardeners in the West generally use the system of 24 climate zones first published by the Sunset Publishing Corporation in the Western Garden Book. The Sunset zone maps (www.sunset.com/garden/climate-zones/climate-zones-intro-us-map-00400000036421 ) factor in not only minimum winter temperatures but also summer highs, growing season length, humidity, and rainfall patterns. The zones correlate to a series of regional maps of the West. Zone 1 represents the harshest growing conditions, zone 24 the mildest.
In 1997, Sunset published its first National Garden Book. Applying the same range of climatic criteria to areas of the United States and Canada east of the Continental Divide, it added 21 new climate zones, zones 25 to 45. Most gardeners in these regions, however, continue to use the USDA map.