Polar climates have temperatures reaching up to -58 degrees Fahrenheit in the winter months, and from 10 to 50 degrees Fahrenheit during summer. Despite these harsh temperatures, about 1,700 species of plants can develop and survive, including sedges, liverworts, reindeer mosses and grasses. However, low temperatures causes the vegetation to grow sparsely.
Soils of polar climates are poor in nutrients and called permafrost because their lower layers remains frozen throughout the year. During winter, permafrost also reaches the surface of the soil. In the short summer or growing season, the topsoil thaws, allowing plants to develop. However, the roots have only a few inches to grow before reaching the frozen soil layers. This limits plant growth, resulting in sparse vegetation.
Annual precipitation in polar climates is low, with an average of less than 250 mm, because the cold air is not able to hold moisture. More than half of this precipitation occurs in the form of snow. Precipitation levels decrease even more in higher latitudes, which indicates areas closer to the poles. The lack of available water limits the grow and spread of the tundra vegetation.
Polar climates have long winters, as summer occurs for less than two months. In addition to cold temperatures, the winter is also the season of low light to complete darkness. Plants are autotrophic organisms, which means that they produce their own food through photosynthesis in the presence of sunlight. Plant growth stops during the winter because of the lack of sun. With the growing season restricted to the short summer period, polar climates cannot develop dense vegetation.