A hardiness zone is a defined geographical area in which a specific category of plant life can grow, according to the climatic conditions, including its ability to withstand certain minimum temperatures of the zone. For example, a plant is described as “resistant to zone 10” which means that the plant can withstand a minimum temperature of -1°C (30 F). A more resistant plant that is “resistant to zone 9” can withstand a minimum temperature of -7 ° C. The concept was initially developed by the US Department of Agriculture (USDA), the system has been adopted by other nations.
It could also be explained as the area in which the plants are grown influences their subsequent development. Plant growth is affected by soil conditions and climate change. That is why when determining the plants must take into account the characteristics of the so-called climatic zones. The intolerance of some plants to the low temperatures can cause irreversible damages.
How to protect plants from the cold
A suitable method to protect the plants from the cold is to cover them to avoid the direct contact with the frost. A brief cold, at times, can be tolerated, but a frost can kill the tissues of many plants in a single night.
According to the characteristics of the plants and their area of origin, they endure a minimum temperature below which they deteriorate and can die. In this sense, the only effective protection in many cases is to move the plants to protected interiors or plants must be covered to avoid direct contact with frost.
It was very difficult to find the hardiness zones for South America. Hardiness zones range from 7 – 13, which I feel are not equal to the Plant hardiness zone of the USDA plant hardiness zones developed by the USRead more on backyardgardener.com