Both experienced and new gardeners alike must face the same question when they are trying to decide what plants to put in their gardens: will they grow in my yard?
All sorts of details should be considered from the condition of the soil to the amount of sunlight reaching the ground before deciding what to plant. The United States Department of Agriculture has taken steps to help with one of those decisions involving how winter hardy a plant might be. In 1960, the agency created a zone hardiness map averaging annual minimum temperatures over a 10-year period at thousands of weather stations throughout North America. In 1990, they updated the map, dividing nine of the 11 categories into “a’’ and “b’’ subcategories, and are in the process of redoing it again in light of warming world temperatures.
As a result, most plants purchased in garden centers give the purchaser information on which zones they are most likely to survive. Each zone varies 10 degrees from the one above and below and displays minimum temperatures likely for that region. Wood and adjacent Rains and Van Zandt counties fall in Zone 7b where the coldest average temperatures fall in the 5 to 10 degree range.
Government efforts helped with cold weather, but did nothing to give a gardener any advice on what plants could take the summer heat in states such as Texas. As a result, in the 1990s, the American Horticultural Society did extensive weather research to prepare a heat zone map for the public.
The nation was divided into 12 zones which show the average number of days each year that a region experiences days when temperatures are above 86 degrees. According to the AHS, it’s at that point when a plant begins to suffer damage from the heat. The zones range from No. 1 where there is less than one heat day to No. 12 where there are more than 210 heat days. Officials are in the process of coding plants for heat tolerance. Some in garden centers may already be tagged for heat zones, but others may not. The zone map was created with the understanding that plants would be getting adequate water at all times.
Wood County falls into Zone 8 which has 90 to 120 average days per year above 86 degrees. Van Zandt and Rains counties are also in Zone 8, except for a small island of land that straddles a portion of the Sabine River which serves as a border between the two counties. That area falls in Zone 9 where average days above 86 degrees range from 120 to 150.
With all that said, there are exceptions to the rules. In an individual yard, a gardener might be able to plant a flower that needs warmer temperatures than listed for that zone, if he or she puts it on the south side of the house or near rocks or concrete which tends to hold heat in the winter. Or plants labeled for colder climates just might make it on the north side of the house or in shade. The slope of the land, the density of shade and the depth bulbs are planted all can make a difference in whether the plant lives or dies. Sometimes it boils down to trial and error.
For further information contact:
U.S. National Arboretum www.usna.usda.gov and click on gardens and horticulture
American Horticultural Society www.ahs.org/publications/heat_zone_map.htm