The growing season in every location is governed by several factors: temperature, amount of sunlight and frost. All are related and yet have their own distinct challenges. Also, the factors of a growing season vary even within specific climates. The degree of frost, levels of light and degree of cold or heat can vary, so every gardener needs to understand the effects of these factors to judge how each will influence their crops.
The growing season for gardens and orchards comes in three basic categories: cold, temperate and sub-tropical. All three have plants that will and won't grow well. For instance, citrus fruit trees need long periods of sunlight and high temperatures. Nothing can be done to force them to grow well in a regular orchard setting in a cold climate. Artificial growing atmospheres, such as greenhouses, can combat some of the aspects of an inappropriate climate.
Growing seasons for both vegetables and fruit center around the level of sunlight available. The longer the amount of natural daylight, the hotter the temperature, the less likely nighttime temperatures will drop enough to cause a frost. The degree of sunlight and its relation to temperature depends on the location of a garden in relation to the equator.
In each of the categories of the growing season are "hardiness zones." Zones break down the growing season factors of temperature, the amount of sunlight and frost even further. The colder the zone, the shorter the growing season and the hardier a plant has to be to tolerate the climate. In the United States there are 10 hardiness zones. Globally, there are 13 zones.
The growing season is affected by the location of the garden or fruit orchard in many ways. Extreme shade will lower temperatures and make growing sun-loving plants nearly impossible. Extreme shade will either eliminate the possibility of a plant growing or shorten the time plants will grow well.
The growing season depends on the type of plant as much as the climate and location. Cold-weather plants such as lettuce, radishes, onions and peas will wither, bolt or refuse to grow in the middle of summer. Tomatoes, squash, broccoli, peppers and other heat-loving plants need a long, hot summer to produce a good crop. Likewise, cold-tolerant plants will do well in colder zones and may not grow at all in the hottest climates.
The length of growing seasons also follows the hardiness zone pattern. Hotter climates have longer growing seasons. Some plants take longer to develop and won't reach maturity in a short growing season.