Majulah entrepreneur muda Indonesia : Deskapahendri 2010

Whether you are a novice or an experienced short-season gardener, consulting a plant hardiness zone map will help you to determine which perennial herbs are sufficiently hardy to survive winters in your area.

The plant hardiness zone map for North America shown on page 6 is a modification of a widely used climate-zone map prepared by the US Department of Agriculture. This map, which is based on minimum winter temperatures, divides the United States and Canada into climate zones, of which zones 1 through 10 are shown in the map. Each climate zone is divided from the next by a difference of 5.6° C (10° F). Lower zone numbers indicate lower minimum winter temperatures.

Each of the perennial herbs profiled in the “Culinary Herb Compendium” includes a reference to the coldest zone tolerated by the plant. To find out whether a particular herb may be winterhardy enough for your location, look at the map to find your gardening area. Then match the map color for your location to the map key to determine the hardiness zone you live in. Note, however, that the hardiness zone listings are based on general temperature trends. Neither the hardiness zone map nor the plant hardiness listings necessarily reflects the conditions peculiar to your garden or your immediate area. You may find, for example, that you can grow a particular herb a zone north of its stated maximum limit simply by varying its microclimate, that is, the climate in the plant’s immediate vicinity.

Local factors, such as the amount of snow cover, can also alter the significance of minimum winter temperatures. Snow cover decreases the extent that frost penetrates into the ground, so if you live in an area with consistently heavy snow, your garden may be warmer, from a plant’s perspective, than the hardiness zone map would indicate. Conversely, if you live in an area that experiences mid-winter thaws that melt the snow cover, you may be warmer, but the range of herbs you can grow will be more limited compared to those areas where snow stays all winter.

Finally, hardiness zones should not be considered to be sharp like political boundaries, as this could lead to the absurd prediction that the south side of some gardens bisected by the map lines could grow some herbs that could not be grown on the north side.

Given the limitations of hardiness zone maps, you may wonder why you should be especially concerned about plant hardiness listings. While you can do much to help your outdoor herbs survive the cold season, you can only compensate for minimum winter temperatures to a limited extent. And while minimum winter temperature alone is probably not sufficient to predict a plant’s hardiness limits, it remains the most important factor in determining whether a perennial species will survive in a given region. So do treat plant hardiness listings as flexible guidelines, but know that there simply is not a better predictive system at present.