Colorado Planting Zone Map: What Is A Planting Zone?

A growing zone is defined as a range of temperatures and soil types suitable for growing certain crops or other plants. There are two basic kinds of zones; temperate and tropical. Plants grown in the tropics experience warmer summers than those in temperate areas, but they do not have to deal with frost every winter. Plants grown in the temperate zones, however, must endure cold winters and hot summers.

Plants grown in the tropics usually grow well at both high latitudes (above 30° North latitude) and low latitudes (below 60° South latitude). Plants grown in the temperate zones generally prefer higher latitudes and lower latitudes. Some plants will thrive only where there is a moderate amount of moisture year round while others require constant water.

The zones differ from one region to another because of differences in climate. For example, some regions have mild climates during the summer months and cool, wet winters. Other regions experience dry summers and long periods of rain.

The difference between these two extremes is called a “growing season.” During the growing season, plants receive equal amounts of sunlight throughout their growth cycle. When it comes time to flower or fruit, however, plants need more light than they received when they were young.

Most plants cannot tolerate a summer that is either very hot or dry. The term “extreme” is used to categorize areas in which temperatures stay below or above the average, even during the summer. In some places, summer temperatures do not get hot enough for fruits and vegetables to mature.

Other places may have long periods of frost during the winter. These places will experience a shortened growing season and are categorized as an “exteme”.

Plants grow best within a range of temperatures during the day and night. This is called the “comfort zone.” Most plants cannot tolerate a temperature change greater than about 10 degrees F (6 degrees C) within a 24-hour period.

When it gets much hotter or colder than this, growth will be slowed or stopped completely.

There are two main types of growing zones: A and B. Each is split into two sub-categories, a and b. A places experience the harshest winter weather, while B places have warmer winters.

Planting zones are set based on the average annual extreme minimum temperatures. The average minimum temperature is assumed to be 30 degrees F (-1 degrees C). If the region normally gets colder than this, the plant will not grow there.

The letters at the beginning of each zone (T for tropical, M for Mediterranean, etc.…) are based on the Koppen Climate Classification System. Each letter group is described below:

Colorado Planting Zones – USDA Map Of Colorado Growing Zones on

T means the average temperature never drops below 50 degrees F (10 degrees C). These regions have no freezing weather during the year.

M means the average temperature never gets warmer than 70 degrees F (21 degrees C). Most of the rain falls during the winter.

C means the average temperature is between 50 and 70 degrees F (10 and 21 degrees C). Some plant growth is possible at times during the year, but the winters are still fairly cold and some plants may not be able to withstand the weather.

H means the average temperature stays below 50 degrees F (10 degrees C) and most of the rain falls between October and March.

B means an average temperature between 40 and 50 degrees F (4 and 10 degrees C). Some crops, such as grains, will grow in these climates.

B, SB, S, and W are sub-divisions of B. These each signify the seasonal temperature variation within the major growing zone. S means that the temperature drops by at least 20 degrees F (11 degrees C) between winter and summer.

The temperature difference is not as great in B or other sub-divisions of B. W means the region has a winter with an average low temperature below 32 degrees F (0 degrees C).

Tropical/Equatorial Climate Zones

Tropical climates exist in the equatorial region of the world. These places have a constant temperature throughout the year. It is never too hot or too cold.

Colorado Planting Zones – USDA Map Of Colorado Growing Zones at

Tropical rainforests are located near the equator. They receive almost constantly rainfall. Most rainforests grow on mountains, where the elevation helps to keep temperatures from rising too high.

Rainforests have the greatest biodiversity of any ecosystem. This means they have the most species of plants and animals.

Tropical deserts are located in low-lying areas near the equator. They do not receive much rainfall and can have extreme heat. The Gobi Desert is an example of a tropical desert.

Some places may have a tropical wet and dry climate. These regions have a monsoon season during which a great deal of rainfall occurs. During the rest of the year, there is little rainfall.

Mediterranean Climate Zones

These zones are located between the tropics and the higher latitudes. They surround the world between the Tropic of Capricorn and the Tropic of Cancer (23.5 degrees north and south of the equator).

Mediterranean climates have cool winters and hot summers.

In these regions, there may be high snowfall in the winter or rainy periods in the late fall or early spring. The summers are hot and dry.

The three types of mediterranean climates are Mediterranean climate, Cool Mediterranean climate, and Alpine Climate.

People in these regions may experience allergies from the pollen of plants such as alder, poplar, and birch. These types of plants are common in mediterranean climates.

People who live in a Mediterranean climate have to deal with fires caused by lightning strikes during the dry summer months. These fires can burn large areas of land.

Cool mediterranean climates are similar to the regular mediterranean climate except they experience average high temperatures between 55 and 75 degrees F (13 and 24 degrees C). These areas also experience less than 22 inches (55 centimeters) of rainfall a year.

Alpine Climate Zones

Colorado Planting Zones – USDA Map Of Colorado Growing Zones |

These zones are at high altitude. This means they are usually located up mountains. The temperature rarely rises above 50 degrees F (10 degrees C).

Some alpine climates, called subpolar alpine zones, have long winters and experience snowfall.

Humid Subtropical Climate Zones

These zones are located around the world at latitudes slightly higher than the tropics. They surround the world near the Tropic of Cancer and the Tropic of Capricorn (23.5 degrees north and south of the equator).

Humid subtropical climates are usually located near bodies of water such as oceans, large lakes, and rivers. This type of climate is common in the southeastern United States,southern China, and southeastern Australia. The summers are hot and wet while the winters are mild and dry.

Rainfall is high during the summer months and moderate at other times of the year.

The southwest United States has a similar climate. The winters are slightly colder and the summer is slightly hotter. This type of climate is also common around the Gulf of Mexico and in central Chile.

In these regions, a large portion of the rain that falls evaporates before it can reach the ground. This is called evapotranspiration. In some places, it can be over 100 inches (2,540 millimeters) a year.

Most of the rainfall occurs during the summertime. The winters are usually dry, and most plant life dies back during this time. Trees are scarce in these regions.

People in humid subtropical climate zones have to adapt to the hot and humid summers and the mild winters. They often have to prepare for hurricanes, tropical storms, tsunamis, and other types of severe weather.

Humid Subtropical Forest Zones

These zones usually have a large number of trees. The soil is fertile and there is plenty of rainfall throughout the year.

Sources & references used in this article:

Colorado rare plant field guide by S Spackman, B Jennings, J Coles… – … by the Colorado …, 1997 –

USDA-ARS Colorado maize water productivity data set by TJ Trout, WC Bausch – Irrigation science, 2017 – Springer

Tree regeneration and future stand development after bark beetle infestation and harvesting in Colorado lodgepole pine stands by BJ Collins, CC Rhoades, RM Hubbard… – Forest Ecology and …, 2011 – Elsevier

Forest vegetation of the Colorado front range by RK Peet – Vegetatio, 1981 – Springer

Soil organic carbon concentrations and stocks on Barro Colorado Island—Digital soil mapping using Random Forests analysis by R Grimm, T Behrens, M Märker, H Elsenbeer – Geoderma, 2008 – Elsevier

A spatially-explicit reconstruction of historical fire occurrence in the ponderosa pine zone of the Colorado Front Range by RL Sherriff, TT Veblen – Ecosystems, 2007 – Springer



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