Seeds of Change
As community gardens sprout up along the barrier islands of the Outer Banks, it is no small feat for gardeners to keep these plots of land thriving, and no matter how green your thumb may be, it is helpful for home gardeners to know which Plant Hardiness Zone they are in order for any garden to take root.
Since 1990, the USDA has updated its Plant Hardiness Zone Map (PHZM) twice, the most recent update just occurred in 2012 making this year’s seed packets the first to feature the new map. The updated zone map is a result of using temperature data measured at a greater number of weather stations and over a longer period of time: 30-years or from 1976-2005. In comparison, the 1990 map was based on temperature data from only a 13-year period of 1974-1986, the USDA reported.
“This is the most sophisticated Plant Hardiness Zone Map yet for the United States,” said USDA Undersecretary for Research, Education and Economics, Dr. Catherine Woteki in a press release after the 2012 release of the new map. “The increases in accuracy and detail that this map represents will be extremely useful for gardeners and researchers.”
Zones range from 1, being the coldest, to zone l3, being the warmest. Each zone, is a 10-degree Fahrenheit band and is further divided into 5-degree Fahrenheit zones labelled A and B. Much of eastern North Carolina lies in zone 8A or 8B, which means the region can experience average winter lows between 10 and 20 degrees. While these zones serve only as guidelines, they are helpful in deciding which plants will prosper in your garden and which ones will not, according to the North Carolina Cooperative Extension Center.
You can find the zone map on the back of seed packets or plant tags and gardeners know to use these zones as guidelines when buying seeds or seedlings. Knowing your zone also helps gardeners know when to start seeds and when to transplant them outdoors. For example, if you want a perennial to thrive year after year, you have to choose one that is able to handle a plant hardiness zone 8 climate.
Whether you believe in climate change or not, the 2012 zone map varies from the 1990 map in two key ways: most zone boundaries have shifted, making them a half-zone warmer by 5-degrees Fahrenheit. Nearly entire states, such as Ohio, Nebraska, Indiana and Texas, have shifted one full hardiness zone, or 10 degrees warmer. Some areas around the country have even warmed by two full zones.
Previously, the “hottest” zone was zone 11. Two, even warmer zones, (numbered 12 and 13) had to be added to reflect more extreme temperatures. These additional “frost-free” zones appear in Hawaii and Puerto Rico.
The map released in 2012 is an internet-friendly Geographic Information System (GIS)-based interactive format and features a “find your zone by ZIP code” function, the USDA announced at its unveiling. Static images have also been included.
Gardeners use the map as a tool, but it cannot address all the issues that affect whether a plant thrives or not – such as snow cover, freeze cycles, sunlight, soil moisture and other factors. Extreme temperatures or sudden changes in temperature could also damage or kill a plant in a zone where it would typically thrive. Seedling plants need to adjust to temperature change slowly, according to data from the cooperative extension center.
Being in Zone 8 means Outer Bankers enjoy a long growing season; however, we may experience extreme temperatures of more than 100 degrees Fahrenheit. Tomatoes, bell and hot peppers, corn, okra, lima beans, summer squash, zucchini, cucumbers and melons are a few plants that do well in this zone. According to gardening websites, these seeds should be started indoors four to six weeks before transplanting. Planting should then occur in April and early May and tomatoes and peppers should grow until the first frost comes. Cucumbers and green beans can be replanted in midsummer for a second harvest. Because of the long growing season, gardeners may grow two or even three crops yearly–cool season crops in spring and fall, and warm season crops in summer. According to www.gardenguides.com, cool-season crops such as lettuce and broccoli can typically be grown in the spring and fall in this zone.♦