Köppen Climate Classification - BWk - Cold Desert

Ruth Ann Reyes

Latitudes: Mostly between 30° and 50° north and south latitude.

 

Temperatures: Usually having hot (or warm), dry summers. Tending to have cold, dry winters. Snow is rare, but possible.

 

Precipitation: Arid. Unreliable rainfall. Usually drier than hot deserts.

 

Relevant geography: Often found in temperate zones at higher altitudes than dry deserts. Usually caused by a rain shadow effect from high mountains.

 

USDA equivalent zones: Anywhere from zones 3-10, but usually within zones 7-9.

 

Soil: Very little organic matter. Usually sandy and unable to hold water. May contain layers of clay or rock-hard limy layers (not unlike cement). Typically very high in calcium carbonate and phosphate, making it infertile. Most desert soils are highly alkaline.

 

Dominant plant life of the region: Xerophytic vegetation. Often barren, rocky, or sandy surfaces.

 

Strengths/challenges for plant life: Heat can be a challenge in some of these deserts. Dryness is definitely a challenge. Soils need to be enriched for fertility and pH. Pressure from fungal attacks is not as great. However, when they occur, plants may have less defenses against them. Shade cloth and windbreaks may also be needed to protect plants. And the rare rains can cause flash flood that can wash away crops.

 

Garden plants that are a good fit for this region: Most common plants can be grown, with correct preparation and care. Short season varieties will have an advantage. Prickly pear cactus.

 

Dominant animal life (or its features): Highly adapted to lack of water.

 

Challenges for animal raising: Lack of water.

 

Animals that are a good fit for this region: Goats, donkey, camel, sheep, guinea fowl.

 

Summary

Most people associate deserts with scorching heat. You and I know that’s not always the case. Generally located between 30° and 50° north and south latitude, the cold desert climate is far enough removed from the equator to have a more relaxed heat profile.

 

Summers days may be either warm or hot. Yet your climate has very little, if any, cloud cover to reflect heat. This means that the land will absorb heat all day, charging up like a battery. At night, however, this lack of cloud cover allows that heat will be lost rapidly, creating wide temperature swings between day and night.

 

In the winter, you can expect 1 month, at minimum, with an average temperature below freezing. Most cold deserts fall within USDA plant hardiness zones 7-9, though some span from 3-10.

 

Heat misconceptions aside, deserts are definitely dry. Air humidity is very low with unreliable rainfall. Believe it or not, cold deserts are usually even drier than hot deserts. 

 

But why are deserts so dry? Most deserts are dry because of a phenomenon called “rain shadow”. This is where a mountain forces air up to get over it, thus cooling the air. Cold air can’t hold as much moisture as warm air, so the water vapor turns back to liquid and rains out. The cold, dry air then descends on the other side of the mountain. This dry air has no moisture left to give. As the air warms back up, it acts like a dry sponge, greedily soaking up any moisture the land has to offer. Cold deserts are often located at high elevations, just on the dry side of a mountain’s rain shadow.

 

All life in the desert has adapted to deal with the lack of humidity. Animals have strategies for maximizing water efficiency. Some may even go dormant between rains. Plants, where they can get their roots in through the rocks and sand, have will often have thick skin to prevent water loss. They may have the ability to remain dormant for long periods, or short life cycles to grow and reproduce within the short periods of wetness.

 

Desert soils contain very little organic matter. It is often sandy and may contain clay or cement-like limy layers. Most deserts soils are highly alkaline, typically being very high in calcium carbonate and phosphate, rendering them infertile for most uses. Some scientists don’t even classify dessert soil as a true soil, due to its lack of organic matter.

 

I’ll admit that I may not have painted the most favorable picture for anyone wanting to grow food in the desert. But for most residents in the cold desert, these are merely challenges, not a gardening death knell.

 

Your primary challenges are too much heat, too much sun, lack of water, and lack of soil fertility. The first two are related, so let’s start with those.

 

Not all cold deserts have hot summers. For those that do, the heat can really hit your plants hard. For you, the best time to garden may be spring and fall. For those with less heat, summers are fine for gardening. Even if your summer is only warm, you may still want to consider shade cloth. Ultraviolet light can be very intense under a desert sky and may be too much for plants.

 

Watering can also help to cool the soil and cool your plants. Always water your plants deeply. Encourage the roots to grow down as deep as possible. Shallow roots are more vulnerable to drying out and heat.

 

Deserts around the world are farmed successful with strategic irrigation and careful plant selection. Avoid wasteful practices. Every drop counts.

 

Winters are more of a challenge in the cold deserts desert than hot. However, you may be able to grow cool season plants with nothing more than a cold frame or by planting in trenches covered with a plastic sheet.

 

The desert does not harbor many of the fungi or insect pests that are dangerous to garden plants. However, they will move in if you let them. Be vigilant, and use smart gardening techniques like crop rotation and sanitary pruning strategies.

 

Soil is another vital consideration. Desert soils will absolutely require amending - possibly replacing. They are high in salts, highly alkaline, and have none of the fertility your plants will need. Some areas may be easy to work with at surface level, but will have a rocklike layer below that will stop plant roots and prevent drainage. Dig down to make sure your plant’s roots have enough room to grow. Then fill that hole with good soil.

 

Soil fertility can be built over time, but it’s easiest if you start with the good stuff and work on maintaining it.

 

You might also consider windbreaks. Desert winds can be damaging in themselves, but sand particles and other debris can seriously tear up your plants.

 

Lastly, you should be aware of the danger of flash floods. This sounds counter-intuitive, I know. But the rare rains of the desert may generate garden-destroying flows of water. If you get the opportunity, go outside when the rain is falling and observe the flow of water across the ground. Which areas seem protected and which ones could be in danger? Plan your garden accordingly.

 

Selecting Plants and Animals for the Desert

When gardening in the desert, plant selection is very important. For starters, shorter season varieties are usually a better choice than varieties that take a long time to mature. Growth may be slowed or halted by extremes of temperature, extending the expected time to maturity. But while the plant is waiting, bugs won’t be.

 

Avoid varieties that thrust their fruit out into the air. These are pretty and easy to harvest, but they are too exposed. Choose varieties that hide their fruit under the canopy of their leaves. If your desert summers are too hot for most other plants, try squash, watermelon, and cantaloupe. They love the heat.

 

Most conventional garden plants don’t want to grow in the desert. You can put in the work to make the environment more suitable for them. Alternately, you could select plants that are already adapted to desert conditions. This will limit your options, but you’ll still find some winner. Prickly pear cactuses, for example, come in several varieties. Many are quite attractive and all produce edible pads and fruit.

 

Raising animals in the desert also requires some strategy. There’s a reason you don’t find polar bears in Arizona, and it’s not because they’re really good at hiding.

 

Donkeys and camels excel in desert environments. They are typically used as work animals, though both are popular as food in some parts of the world. If you’re looking for a more conventionally accepted food animal, consider goats. The Boer and Myotonic breeds excel in arid climates and are bred for meat. Nubian and Nigerian Dwarf goats are raised for milk and can also handle arid conditions. Sheep bred for arid regions may also be acceptable, but can’t approach a goat’s foraging tenacity.

 

Some chicken breeds, such as Easter Eggers, are suited to hot environments. However, you might also consider guinea fowl. Helmeted guineas are extremely hardy and well adapted to the climate. They can be raised for meat and eggs, and are generally more wary of predators.

 

Greening the Desert

Just as lush areas can gradually become deserts through over-farming and unsustainable agricultural practices, environmentally friendly practices can reverse desertification, gradually making this region wetter and greener.

 

The desert cycle is largely self-perpetuating. The heat and dryness make it hard for plants to grow. Without plants, especially trees, the ground absorbs more and more of the sun’s energy. This heats the air, which reduces precipitation. The less it rains, the more difficult it is for plants to grow.

 

The shade from trees cools the ground, reducing evaporation. This makes it easier for other plants to grow. They also reflect some of the sun’s heat back out into space, creating further cooling. Cooler land means cooler air. Cooler air absorbs less moisture from the environment and is more likely to create rain. 

 

The addition of organic matter from the trees, and from the life that comes in with them, will help make the soils more fertile. Increased precipitation will help balance the soil’s pH by washing away the excess alkalizing minerals salts.

 

Greening deserts can help make local climates more hospitable and could make it possible for us to grow more food across the planet.