Knowing the length of the growing season by using information gleaned from the USDA Plant Hardiness Zone Map and the AHS Plant Heat Zone Map is very important to successful gardening. This enables the gardener to make wise choices when choosing fruits, flowers, trees and vegetables for their specific geographical area. It is knowing the average number of days between last frost in the spring and the first frost in the fall that allows gardeners to choose vegetables that will mature in their zone before a killing frost in the fall puts the garden to bed for the winter. This information can mean the difference between harvesting a bumper crop of cantaloupe or eating a supermarket melon.
Other factors for successful growing in any gardening situation are soil conditions, rainfall or the lack of it, good drainage, humidity, air circulation and soil fertility. Growing conditions vary from year to year. Some years late spring frosts make replanting tender plants a necessity or an early fall frost can blacken a row of green beans that are just setting on pods.
While it is smart to choose plants labeled for your growing area, there are ways to outwit Mother Nature. Within a landscape there may be smaller microclimates such as the south side of a brick home or raised beds. These areas warm up faster in the spring, allowing for extra growing days compared to another location in the same landscape. Cold frames against the south side of a garden shed extend the salad crop into the winter months. The use of hot caps, plant protectors filled with water and floating row covers extend the growing season at both ends. What works one year may not be applicable in another year, but any attempt at fooling Mother Nature sometimes pays great growing dividends.
Cold isn’t the only factor to limit success in the landscape. Heat has negative effects as well, although the effects are more subtle and harder to diagnose. Extreme cold will kill a plant quickly but heat sometimes drags it out to a slow death over many weeks. Flower buds fail to open, raspberry blossoms dry up, tomatoes fail to set fruit and general stunting is obvious. The American Horticultural Society has created another map, the Heat-Zone Map available at their website, just as helpful and valuable to the gardener as the hardiness map. This map consists of 12 zones that tell us the average number of days each year that exceeds 86 degrees. Physiological damage from heat begins at that point. The AHS Heat-Zone ratings assume the plant has adequate water at all times. This number is measuring heat days and has nothing to do with drought conditions. Failure to water a plant according to it’s specific cultural requirements means a dead plant, regardless of the zone number. Some plants can tolerate a drought more than others, but no plant can survive complete desiccation. Know what the specific water requirements are for the desired plants and be prepared to supplement water during times of drought.
Understanding the Plant Hardiness Zones and AHS Heat-Zone Map will make catalog choices easier and translates to successes in the landscape. It means food on the table and flowers in the borders. Memorize these numbers and shop and grow with confidence.
Learn more tips to becoming a successful gardener at Do It YourSelf Gardening.