By Darrell Blackwelder
For The Salisbury Post
Whenever you buy a plant or shrub at your local garden center, most are tagged with minimal growing instructions. However, most all will have numerical hardiness zone is almost always included on the information tag, especially when the plant is grown out of state.Gardeners have relied on this hardiness information for more than 40 years as a standard guide to plant cold tolerance. These zones are a way to determine if a plant will survive in our area based research by the USDA on climatic zones in the United States.
These zones are divided into 11 areas based on a 10-degree Fahrenheit difference in the average annual minimum temperature. The temperature information on which the map is based came from about 7,000 weather stations that could be identified by latitude and longitude. Zones in the United States fall within Zones 2 through 10. The lowest average temperature in Zone 2 is -50 to -40 degrees Fahrenheit, while the minimum average temperature in zone 10 is +30 to +40 degrees Fahrenheit.
North Carolina hardiness zones range from zone 6 in the mountain areas to zone 8 in the coastal areas. Rowan County and the Piedmont falls into plant hardiness zone 7. Actually, Rowan County is split into Zones 7-A and 7-B. Zone 7-A is the Woodleaf Cleveland area. Plants in this zone are hardy from 0-5 degrees. Zone 7-B, the southern end of the county, is warmer, able to survive temperatures from 5-10 degrees.
Suggested hardiness zones for plants have been researched for years by USDA scientists and horticulturalist to enable both growers and the public purchase plants that will survive their location.
Many tags will give a range of zones ó for example, this plant has suitable hardiness for zones 4-9. This means the tree or perennial is known to be hardy in zones 4, 5, 6, 7, 8, and 9. Suitable hardiness means a plant can be expected to grow in the zone’s temperature extremes, as determined by the lowest average annual temperature.
Keep in mind that local variations such as moisture, soil, winds, and other conditions might affect the viability of individual plants.