Will It Survive in Your Garden?
Judy Ziemba, State Chairman

After meeting the appropriate soil, light and water requirements of plants, you must also consider the hardiness of the plant in your garden. Based on many years of weather statistics, the USDA established a map of cold hardiness zones. This was done in 1966 then most recently updated in 1990. The country was divided into ten zones with further subdivisions of A and B based on the average lowest temperatures recorded. Illinois is divided into Zones 4 through 6 reflecting average lowest temperatures of -20 F. to -30F for Zone 4 to 0F. to -10F. for Zone 6.

For a number of years the weather statistics have indicated a trend to milder temperatures, which has fueled the global warming discussion. Elders are famous for saying how the weather was much worse when they walked x number of miles to school. Others claim the current weather patterns are part of the natural ebb and flow of climate and should not be cause of concern.

The USDA is proposing an updated cold hardiness zone map that should released later this year. The A and B divisions will be eliminated and zones will be numbered one through 15. The additional zones will reflect the semitropical portions of the U.S. The USDA has contracted with the American Horticulture Society to provide data and create the map. It will be quite sophisticated as it will be digital with layered data to reflect elevations and lake effects and allow users to find details to the county level. Keep in mind this map will reflect over 50 years of data.

The National Arbor Day Foundation has opted to propose their own version of Cold Hardiness Zones based on fifteen years of data from the 5000 National Oceanic and Atmospheric Administration's data centers in the U.S. The new Arbor Day map is consistent with the climate scientists who state global warming is happening. Arborists contend that tree planting is a good way to counteract this trend. Their website allows tree planters to enter a zipcode and be given up-to-date information. It may also indicate the existing tree species that may be stressed in warmer climates and can be monitored. Basically, the Arbor Day Foundation is encouraging planting diverse species to insure future tree health. As gardeners we might also improve diversity by planting native species. An experience with a nursery employee trying to sell me a "new improved" shrub listed one zone higher than recommended causes me to question the objectivity of the Arbor Day Foundation. Trees do remove tons of CO2 and release O2. They act as windbreaks and provide shade to reduce air-conditioning needs, but they must be strategically placed and vigorous specimens.

Many serious gardeners have succumbed to "zone envy" (planting plants too tender for their garden) and are easily persuaded to grow and promote unusual plant material while using microclimates. Nurseries have a fine line to walk between developing hardier versions of plant stock and promoting plants that have limited hardiness in their retail selling area thereby requiring replanting. Fortunately, gardening is a process and as better cultivars are introduced, all gardeners are in a better position to design and beautify their living areas. Any information that helps us decide "the right plant in the right place" cannot be disregarded, especially in placing plants we hope to leave to future generations.